##### Table of Contents









UNITED STATES


SECURITIES AND EXCHANGE COMMISSION


Washington, D.C. 20549





Form 10-K


(Mark One)


þ


ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF


THE SECURITIES EXCHANGE ACT OF 1934


For the fiscal year ended December 31, 2005


OR


o


TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)


OF THE SECURITIES EXCHANGE ACT OF 1934


For the transition period
from        to


Commission File Number 1-4874


Colorado Interstate Gas Company




|                                                                   |  |                                         
|------------------------------------------------------------------ |  | ----------------------------------------
|Delaware                                                           |  | 84-0173305                              
|(State or Other Jurisdiction of
    Incorporation or Organization) |  | (I.R.S. Employer
    Identification No.)
|                                                                  
|El Paso Building                                                   |  |                                         
|1001 Louisiana Street
    Houston, Texas                           |  | 77002                                   
|(Address of Principal Executive Offices)                           |  | (Zip Code)                              

Telephone
number:  (713) 420-2600


Securities registered pursuant to Section 12(b) of the
Act:


|                                  |  |                                          
|--------------------------------- |  | -----------------------------------------
|Title of Each Class               |  | Name of Each Exchange on which Registered
|                                  |  |                                          
|6.85% Senior Debentures, due 2037 |  | New York Stock Exchange                  

Securities registered pursuant to Section 12(g) of the
Act: None


o þ


o þ


þ o


S-K 10-K 10-K. þ




|                          |  |                     |  |                        
|------------------------- |  | ------------------- |  | -----------------------
|Large accelerated filer o |  | Accelerated filer o |  | Non-accelerated filer þ

12b-2 o þ


State the aggregate market value of
the voting stock held by non-affiliates of the
registrant:    None


Indicate the number of shares
outstanding of each of the registrants classes of common
stock, as of the latest practicable date.




COLORADO INTERSTATE GAS COMPANY MEETS
THE CONDITIONS OF GENERAL INSTRUCTION I(1)(a) AND (b) TO
FORM 10-K AND IS
THEREFORE FILING THIS REPORT WITH A REDUCED DISCLOSURE FORMAT AS
PERMITTED BY SUCH INSTRUCTION.


Documents incorporated by reference: None










---



##### 










COLORADO INTERSTATE GAS COMPANY


TABLE OF CONTENTS


|                                                       |  |                                                                                                                      |  |                                                                                                                                   |    |  |    | 
|------------------------------------------------------ |  | -------------------------------------------------------------------------------------------------------------------- |  | --------------------------------------------------------------------------------------------------------------------------------- | -- |  | -- | 
|                                                       |  | Caption                                                                                                              |  | Page                                                                                                                              |   
|                                                       |  |                                                                                                                      |  |                                                                                                                                   |   
|PART I                                                
|Item 1.                                                |  | Business                                                                                                             |  |                                                                                                                                   | 1  | 
|Item 1A.                                               |  | Risk Factors                                                                                                         |  |                                                                                                                                   | 5  | 
|                                                       |  |                                                                                                                      |  | Cautionary Statement for Purposes of the
    Safe Harbor Provisions of the Private Securities
    Litigation Reform Act of 1995 |    |  |    | 
|Item 1B.                                               |  | Unresolved Staff Comments                                                                                            |  |                                                                                                                                   | 9  | 
|Item 2.                                                |  | Properties                                                                                                           |  |                                                                                                                                   | 9  | 
|Item 3.                                                |  | Legal Proceedings                                                                                                    |  |                                                                                                                                   | 10 | 
|Item 4.                                                |  | Submission of Matters to a Vote of Security
    Holders                                                              |  |                                                                                                                                   | *  | 
|PART II                                               
|Item 5.                                                |  | Market for Registrants Common Equity,
    Related Stockholder Matters and Issuer Purchases of Equity
    Securities |  |                                                                                                                                   | 10 | 
|Item 6.                                                |  | Selected Financial Data                                                                                              |  |                                                                                                                                   | *  | 
|Item 7.                                                |  | Managements Discussion and Analysis
    of Financial Condition and Results of Operations                            |  |                                                                                                                                   | 11 | 
|Item 7A.                                               |  | Quantitative and Qualitative Disclosures
    About Market Risk                                                       |  |                                                                                                                                   | 15 | 
|Item 8.                                                |  | Financial Statements and Supplementary
    Data                                                                      |  |                                                                                                                                   | 16 | 
|Item 9.                                                |  | Changes in and Disagreements with
    Accountants on Accounting and Financial Disclosure                             |  |                                                                                                                                   | 36 | 
|Item 9A.                                               |  | Controls and Procedures                                                                                              |  |                                                                                                                                   | 36 | 
|Item 9B.                                               |  | Other Information                                                                                                    |  |                                                                                                                                   | 36 | 
|PART III                                              
|Item 10.                                               |  | Directors and Executive Officers of the
    Registrant                                                               |  |                                                                                                                                   | *  | 
|Item 11.                                               |  | Executive Compensation                                                                                               |  |                                                                                                                                   | *  | 
|Item 12.                                               |  | Security Ownership of Certain Beneficial
    Owners and Management and Related Stockholder Matters                   |  |                                                                                                                                   | *  | 
|Item 13.                                               |  | Certain Relationships and Related
    Transactions                                                                   |  |                                                                                                                                   | *  | 
|Item 14.                                               |  | Principal Accountant Fees and Services                                                                               |  |                                                                                                                                   | 36 | 
|PART IV                                               
|Item 15.                                               |  | Exhibits and Financial Statement
    Schedules                                                                       |  |                                                                                                                                   | 37 | 
|                                                       |  |                                                                                                                      |  | Signatures                                                                                                                        |    |  | 40 | 
|Certification of CEO pursuant to Section 302          
|Certification of CFO pursuant to Section 302          
|Certification of CEO pursuant to 18 U.S.C Section 1350
|Certification of CFO pursuant to 18 U.S.C Section 1350








|  |                                                                                                                                                                                                   
|- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|* | We have not included a response to this item in this document
    since no response is required pursuant to the reduced disclosure
    format permitted by General Instruction I to
    Form 10-K.



|     |  |                                
|---- |  | -------------------------------
|/d   |  | = per day                      
|BBtu |  | = billion British thermal units
|Bcf  |  | = billion cubic feet           
|LNG  |  | = liquefied natural gas        
|MDth |  | = thousand dekatherms          
|MMcf |  | = million cubic feet           
|NGL  |  | = natural gas liquids          





i



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##### Table of Contents






PART I





ITEM 1. BUSINESS


Overview and Strategy


10-K






Reservation revenues.


Usage revenues.








| |   |                                                 
| | - | ------------------------------------------------
| |  | Favorably resolve our upcoming CIG rate case;   
|
| |  | Successfully recontract transportation capacity;
|
| |  | Focus on cost efficiencies, especially fuel use;
|
| |  | Successfully complete expansion projects; and   
|
| |  | Attract new supply and transport to new markets.



The CIG System.


1



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##### Table of Contents



The WIC System.


24-inch


Storage Facilities.




| |                        
| | -----------------------
| | Markets and Competition







on-system on-system




2



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##### Table of Contents





|         |  |                                                                                                                                                                                                                                     |  |                                                                                                                                                                                                                                                                                              |  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|-------- |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Pipeline |  |                                                                                                                                                                                                                                     |  |                                                                                                                                                                                                                                                                                              |  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|System   |  | Customer Information                                                                                                                                                                                                                |  | Contract Information                                                                                                                                                                                                                                                                         |  | Competition                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|         |  |                                                                                                                                                                                                                                     |  |                                                                                                                                                                                                                                                                                              |  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|CIG      |  | Approximately 111 firm and interruptible customers
    Major Customer:  Public Service Company
    of   Colorado   (970
    BBtu/d)   (187
    BBtu/d)   (261 BBtu/d)                                                               |  | Approximately 184 firm transportation contracts. Weighted
    average remaining contract term of approximately
    five years.
    Contract terms expire in 2007.
    Contract term expires in 2008.
    Contract terms expire in 2009-2014.                                                 |  | CIG serves two major markets. Its on-system market consists of
    utilities and other customers located along the front range of
    the Rocky Mountains in Colorado and Wyoming. Its off-system
    market consists of the transportation of Rocky Mountain
    production from multiple supply basins to interconnections with
    other pipelines bound for the midwest, the southwest, California
    and the Pacific northwest. Competition for its on-system market
    consists of an intrastate pipeline, local production from the
    Denver-Julesburg basin, and long-haul shippers who elect to sell
    into this market rather than the off-system market. Competition
    for its off-system market consists of other existing and
    proposed interstate pipelines that are directly connected to its
    supply sources.
|        
|WIC      |  | Approximately 47 firm and
    interruptible customers
    Major Customers:  Williams Power
    Company    (353 BBtu/d)  CIG    (247 BBtu/d)  Western
    Gas
    Resources    (235 BBtu/d)  Cantera
    Gas Company    (226 BBtu/d) |  | Approximately 47 firm transportation contracts. Weighted
    average remaining contract term of approximately
    six years.
    Contract terms expire in 2008-2013.
    Contract terms expire in 2006-2016.
    Contract terms expire in 2007-2013.
    Contract terms expire in 2012-2013. |  | WIC competes with pipelines that are existing, proposed and
    currently under construction to provide transportation services
    to delivery points in northeast Colorado and western Wyoming.
    WICs one Bcf/d Medicine Bow lateral is the primary source
    of transportation for increasing volumes of Powder River Basin
    supply and can readily be expanded as supply increases.
    Currently, there are two other interstate pipelines that
    transport limited volumes out of this basin.                                                                                                                                                                                                                                                                                                                              



| |                       
| | ----------------------
| | Regulatory Environment





| |   |                                                              
| | - | -------------------------------------------------------------
| |  | rates and charges for natural gas transportation and storage;
|
| |  | certification and construction of new facilities;            
|
| |  | extension or abandonment of services and facilities;         
|
| |  | maintenance of accounts and records;                         
|
| |  | relationships between pipeline and energy affiliates;        
|
| |  | terms and conditions of services;                            
|
| |  | depreciation and amortization policies;                      

3



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##### Table of Contents





| |   |                                               
| | - | ----------------------------------------------
| |  | acquisition and disposition of facilities; and
|
| |  | initiation and discontinuation of services.   







| |              
| | -------------
| | Environmental





| |          
| | ---------
| | Employees



4



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|         |             
|-------- | ------------
|ITEM 1A. | RISK FACTORS




CAUTIONARY STATEMENT FOR PURPOSES OF THE SAFE
HARBOR PROVISIONS OF THE PRIVATE SECURITIES LITIGATION
REFORM ACT OF 1995






Risks Related to Our Business


Our success depends on factors beyond our control.






| |   |                                                                                                                                                                                                   
| | - | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |  | service area competition;                                                                                                                                                                         
|
| |  | expiration or turn back of significant contracts;                                                                                                                                                 
|
| |  | changes in regulation and actions of regulatory bodies;                                                                                                                                           
|
| |  | future weather conditions;                                                                                                                                                                        
|
| |  | price competition;                                                                                                                                                                                
|
| |  | drilling activity and availability of natural gas;                                                                                                                                                
|
| |  | decreased availability of conventional gas supply sources and
    the availability and timing of other gas supply sources, such as
    LNG;                                                       
|
| |  | decreased natural gas demand due to various factors, including
    increases in prices and the increased availability or popularity
    of alternative energy sources such as hydroelectric power;
|
| |  | increased costs of capital;                                                                                                                                                                       
|
| |  | opposition to energy infrastructure development, especially in
    environmentally sensitive areas;                                                                                               
|
| |  | adverse general economic conditions; and                                                                                                                                                          
|
| |  | unfavorable movements in natural gas and NGL prices in supply
    and demand areas.                                                                                                               

5



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The revenues of our pipeline businesses are generated
under contracts that must be renegotiated periodically, some of
which are for a substantial portion of our firm transportation
capacity.








| |   |                                                                                                                                                                                         
| | - | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |  | competition by other pipelines, including the proposed
    construction by other companies of additional pipeline capacity
    in markets served by us;                                 
|
| |  | changes in state regulation of local distribution companies,
    which may cause them to negotiate
    short-term contracts or
    turn back their capacity when their contracts expire;
|
| |  | reduced demand and market conditions in the areas we serve;                                                                                                                             
|
| |  | the availability of alternative energy sources or gas supply
    points; and                                                                                                            
|
| |  | regulatory actions.                                                                                                                                                                     





Fluctuations in energy commodity prices could adversely
affect our business.






| |   |                                                                                               
| | - | ----------------------------------------------------------------------------------------------
| |  | regional, domestic and international supply and demand;                                       
|
| |  | availability and adequacy of transportation facilities;                                       
|
| |  | energy legislation;                                                                           
|
| |  | federal and state taxes, if any, on the transportation and
    storage of natural gas and NGL;
|
| |  | abundance of supplies of alternative energy sources; and                                      
|
| |  | political unrest among oil producing countries.                                               

6



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The agencies that regulate us and our customers affect our
profitability.








Environmental compliance and remediation costs and the
costs of environmental liabilities could exceed our
estimates.


clean-up




| |   |                                                                                                                                                                       
| | - | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |  | The uncertainties in estimating pollution control and clean up
    costs, including sites where preliminary site investigation or
    assessments have been completed;
|
| |  | The discovery of new sites or additional information at existing
    sites;                                                                                           
|
| |  | The uncertainty in quantifying liability under environmental
    laws that impose joint and several liability on all potentially
    responsible parties; and         
|
| |  | The nature of environmental laws and regulations, including the
    interpretation and enforcement thereof.                                                           





7



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Our operations are subject to operational hazards and
uninsured risks.






The expansion of our business by constructing new
facilities subjects us to construction and other risks that may
adversely affect our financial results.






| |   |                                                                                                                                                                                                                                                                    
| | - | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |  | our ability to obtain all necessary approvals and permits by
    regulatory agencies on a timely basis on terms that are
    acceptable to us;                                                                                                                     
|
| |  | potential changes of federal, state and local statutes and
    regulations, including environmental requirements that prevent a
    project from proceeding or increase the anticipated cost of the
    expansion project;                                         
|
| |  | impediments on our ability to acquire rights-of-ways or land
    rights on a timely basis within our anticipated costs;                                                                                                                                            
|
| |  | our ability to construct projects within anticipated costs,
    including the risk that we may incur cost overruns resulting
    from inflation or increased costs of equipment, materials or
    labor, or other factors beyond our control, that may be material;
|
| |  | anticipated future growth in natural gas supply does not
    materialize; and                                                                                                                                                                                      
|
| |  | lack of transportation, storage or throughput commitments that
    result in write-offs of development costs.                                                                                                                                                      



Risks Related to Our Affiliation with El Paso




Our relationship with El Paso and its financial condition
subjects us to potential risks that are beyond our
control.




8



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Our system of internal controls is designed to provide
reasonable assurance regarding the reliability of our financial
reporting and the preparation of our financial statements for
external purposes. A loss of public confidence in the quality of
our internal controls or disclosures could have a negative
impact on us.


decision-making


We may be subject to a change of control under certain
circumstances.




A default under El Pasos $3 billion credit
agreement by any party could accelerate our future borrowings,
if any, under the agreement and our long-term debt, which could
adversely affect our liquidity position.




We are an indirect subsidiary of El Paso.






| |   |                                                                
| | - | ---------------------------------------------------------------
| |  | our payment of dividends;                                      
|
| |  | decisions on our financings and our capital raising activities;
|
| |  | mergers or other business combinations;                        
|
| |  | our acquisitions or dispositions of assets; and                
|
| |  | our participation in El Pasos cash management program.        








|         |                          
|-------- | -------------------------
|ITEM 1B. | UNRESOLVED STAFF COMMENTS






ITEM 2. PROPERTIES






9



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|        |                  
|------- | -----------------
|ITEM 3. | LEGAL PROCEEDINGS



Natural Buttes.







|        |                                                    
|------- | ---------------------------------------------------
|ITEM 4. | SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

10-K.





PART II







|        |                                                                                                                 
|------- | ----------------------------------------------------------------------------------------------------------------
|ITEM 5. | MARKET FOR REGISTRANTS COMMON EQUITY, RELATED
    STOCKHOLDER MATTERS AND ISSUER PURCHASES OF EQUITY SECURITIES










|        |                        
|------- | -----------------------
|ITEM 6. | SELECTED FINANCIAL DATA

10-K.


10



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|        |                                                                                          
|------- | -----------------------------------------------------------------------------------------
|ITEM 7. | MANAGEMENTS DISCUSSION AND ANALYSIS OF FINANCIAL
    CONDITION AND RESULTS OF OPERATIONS

10-K.




Overview










|                |  |           |       |                  |                     |  |    | 
|--------------- |  | --------- | ----- | ---------------- | ------------------- |  | -- | 
|                |  |           |       | Percent of Total |                    
|                |  | BBtu/d(1) |       |                  | Contracted Capacity | 
|                |  |           |       |                  |                     | 
|2006            |  |           | 424   |                  |                     |  | 7  | 
|2007            |  |           | 1,876 |                  |                     |  | 32 | 
|2008            |  |           | 376   |                  |                     |  | 6  | 
|2009 and beyond |  |           | 3,239 |                  |                     |  | 55 | 






|    |                                         
|--- | ----------------------------------------
|(1) | Includes CIG capacity on the WIC system.

11



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Results of Operations




|                                 |                  |                      |       |     |      |   |       |     | 
|-------------------------------- | ---------------- | -------------------- | ----- | --- | ---- | - | ----- | --- | 
|                                 |                  | 2005                 |       |     | 2004 |  
|                                 |                  |                      |       |     |      |  
|                                 |                  | (In millions, except |      
|                                 |                  | volumes amounts)     |      
|Operating revenues               |                  | $                    | 374   |     |      | $ | 348   |    
|Operating expenses               |                  |                      | (227  | )   |      |   | (185  | )  
|                                 |                  |                      |       |     |      |  
|                                 | Operating income |                      |       | 147 |      |   |       | 163 | 
|Other income, net                |                  |                      | 8     |     |      |   | 3     |    
|                                 |                  |                      |       |     |      |  
|                                 | EBIT             |                      |       | 155 |      |   |       | 166 | 
|Interest and debt expense        |                  |                      | (30   | )   |      |   | (26   | )  
|Affiliated interest income, net  |                  |                      | 27    |     |      |   | 13    |    
|Income taxes                     |                  |                      | (55   | )   |      |   | (54   | )  
|                                 |                  |                      |       |     |      |  
|                                 | Net income       |                      | $     | 97  |      |   | $     | 99  | 
|                                 |                  |                      |       |     |      |  
|                                
|Total throughput
    (BBtu/d)(1) |                  |                      | 3,207 |     |      |   | 2,787 |    
|                                 |                  |                      |       |     |      |  




|    |                                                                                                                                                                
|--- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------
|(1) | Throughput volumes include billable transportation throughput
    volume for storage activities and exclude throughput transported
    by WIC on behalf of CIG.



|                                                                 |                      |                         |    |    |         |   |     |       |   |   |        |   |  |   |     |     |  
|---------------------------------------------------------------- | -------------------- | ----------------------- | -- | -- | ------- | - | --- | ----- | - | - | ------ | - |  | - | --- | --- | -
|                                                                 |                      |                         |    |    |         |   |     | EBIT  |  
|                                                                 |                      |                         |    |    |         |   |     |       |  
|                                                                 |                      | Revenue                 |    |    | Expense |   |     | Other |   |   | Impact |  
|                                                                 |                      |                         |    |    |         |   |     |       |   |   |        |  
|                                                                 |                      | Favorable/(Unfavorable) |   
|                                                                 |                      | (In millions)           |   
|Gas not used in operations, revaluations and processing revenues |                      | $                       | 8  |    |         | $ | (28 | )     |   | $ |       |   |  | $ | (20 | )  
|Environmental reserve                                            |                      |                         |   |    |         |   | (13 | )     |   |   |       |   |  |   | (13 | )  
|Higher general and administrative expenses                       |                      |                         |   |    |         |   | (6  | )     |   |   |       |   |  |   | (6  | )  
|Higher transportation revenues                                   |                      |                         | 13 |    |         |   |    |       |   |   |       |   |  |   | 13  |    
|Other(1)                                                         |                      |                         | 5  |    |         |   | 5   |       |   |   | 5      |   |  |   | 15  |    
|                                                                 |                      |                         |    |    |         |   |     |       |   |   |        |  
|                                                                 | Total impact on EBIT |                         | $  | 26 |         |   | $   | (42   | ) |   | $      | 5 |  |   | $   | (11 | )
|                                                                 |                      |                         |    |    |         |   |     |       |   |   |        |  




|    |                                              
|--- | ---------------------------------------------
|(1) | Consists of individually insignificant items.



Gas Not Used in Operations, Revaluations and Processing
Revenues.


12



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##### Table of Contents







Environmental Reserve.


Higher General and Administrative Expenses.


Expansions.


|               |  |                                 |  |           |               |  |                              |                                                                              
|-------------- |  | ------------------------------- |  | --------- | ------------- |  | ---------------------------- | -----------------------------------------------------------------------------
|               |  | Actual/                         |  | Actual/   |               |  |                             
|               |  | Anticipated Completion          |  | Estimated |               |  |                             
|Project        |  | or In Service Date              |  | Cost      |               |  | Estimated Annual Revenues(1)
|               |  |                                 |  |           |               |  |                             
|Raton Basin    |  | September and
    December 2005 |  |           | $54 million   |  |                              | 2006 - $9 million;
    Thereafter - $13 million annually                     
|Piceance Basin |  | March 2006                      |  |           | $132  million |  |                              | 2006 - $11 million; 2007 - $19 million;
    Thereafter - $21 million annually






|    |                                                                                                               
|--- | --------------------------------------------------------------------------------------------------------------
|(1) | Estimated revenues represent executed agreements with third
    parties for capacity on the expansion project.

Accounting for Pipeline Integrity Costs.


Regulatory Matter.


13



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Interest and Debt Expense




Affiliated Interest Income, Net




Income Taxes


|                   |  |                   |    |   |      |   |    |  
|------------------ |  | ----------------- | -- | - | ---- | - | -- | -
|                   |  | Year Ended        |   
|                   |  | December 31,      |   
|                   |  |                   |   
|                   |  | 2005              |    |   | 2004 |  
|                   |  |                   |    |   |      |  
|                   |  | (In millions,     |   
|                   |  | except for rates) |   
|Income taxes       |  | $                 | 55 |   |      | $ | 54 |  
|Effective tax rate |  |                   | 36 | % |      |   | 35 | %



Liquidity and Capital Resources


Liquidity Overview






Debt




14



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cross-acceleration




Capital Expenditures




|                |       |               |     |     |      |   |    |    | 
|--------------- | ----- | ------------- | --- | --- | ---- | - | -- | -- | 
|                |       | 2005          |     |     | 2004 |  
|                |       |               |     |     |      |  
|                |       | (In millions) |    
|Maintenance     |       | $             | 29  |     |      | $ | 36 |   
|Expansion/Other |       |               | 119 |     |      |   | 25 |   
|                |       |               |     |     |      |  
|                | Total |               | $   | 148 |      |   | $  | 61 | 
|                |       |               |     |     |      |  



Commitments and Contingencies




New Accounting Pronouncements Issued But Not Yet Adopted


New Accounting Pronouncements Issued But
Not Yet Adopted





ITEM 7A. QUANTITATIVE AND QUALITATIVE DISCLOSURES
ABOUT MARKET RISK




|             |                                                               |                                |   |     |                   |   |   |          |  |  |       |     |  |  |   |     |  | 
|------------ | ------------------------------------------------------------- | ------------------------------ | - | --- | ----------------- | - | - | -------- |  |  | ----- | --- |  |  | - | --- |  | 
|             |                                                               | December 31, 2005              |   |     | December 31, 2004 |  
|             |                                                               |                                |   |     |                   |  
|             |                                                               | Carrying                       |   |     | Fair              |   |   | Carrying |  |  | Fair  |    
|             |                                                               | Amount                         |   |     | Value             |   |   | Amount   |  |  | Value |    
|             |                                                               |                                |   |     |                   |   |   |          |  |  |       |    
|             |                                                               | (In millions, except for rate) |  
|Liabilities: |                                                               |                                |   |     |                   |   |   |          |  |  |       |     |  |  |   |    
|             | Long-term debt, including current maturities  fixed
    rate |                                | $ | 700 |                   |   | $ | 710      |  |  | $     | 310 |  |  | $ | 320 | 
|             |                                                               | Average interest rate          |   |     | 6.5               | % |   |          |  |  |       |     |  |  |   |     |  | 

15



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ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY
DATA


COLORADO INTERSTATE GAS COMPANY


CONSOLIDATED STATEMENTS OF INCOME


(In millions)


|                                             |                                          |                         |     |     |      |   |     |      |  |   |     |    |  
|-------------------------------------------- | ---------------------------------------- | ----------------------- | --- | --- | ---- | - | --- | ---- |  | - | --- | -- | -
|                                             |                                          | Year Ended December 31, |    
|                                             |                                          |                         |    
|                                             |                                          | 2005                    |     |     | 2004 |   |     | 2003 | 
|                                             |                                          |                         |     |     |      |   |     |      | 
|Operating revenues                           |                                          | $                       | 374 |     |      | $ | 348 |      |  | $ | 347 |   
|                                             |                                          |                         |     |     |      |   |     |      | 
|Operating expenses                           |                                          |                         |     |     |      |   |     |      |  |   |     |   
|                                             | Operation and maintenance                |                         |     | 169 |      |   |     | 130  |  |   |     | 95 |  
|                                             | Depreciation, depletion and amortization |                         |     | 43  |      |   |     | 41   |  |   |     | 34 |  
|                                             | Gain on sale of long-lived assets        |                         |     |    |      |   |     |     |  |   |     | (6 | )
|                                             | Taxes, other than income taxes           |                         |     | 15  |      |   |     | 14   |  |   |     | 12 |  
|                                             |                                          |                         |     |     |      |   |     |      | 
|                                             |                                          |                         | 227 |     |      |   | 185 |      |  |   | 135 |   
|                                             |                                          |                         |     |     |      |   |     |      | 
|Operating income                             |                                          |                         | 147 |     |      |   | 163 |      |  |   | 212 |   
|Other income, net                            |                                          |                         | 8   |     |      |   | 3   |      |  |   | 25  |   
|Interest and debt expense                    |                                          |                         | (30 | )   |      |   | (26 | )    |  |   | (26 | ) 
|Affiliated interest income, net              |                                          |                         | 27  |     |      |   | 13  |      |  |   | 9   |   
|                                             |                                          |                         |     |     |      |   |     |      | 
|Income before income taxes                   |                                          |                         | 152 |     |      |   | 153 |      |  |   | 220 |   
|Income taxes                                 |                                          |                         | 55  |     |      |   | 54  |      |  |   | 83  |   
|                                             |                                          |                         |     |     |      |   |     |      | 
|Income from continuing operations            |                                          |                         | 97  |     |      |   | 99  |      |  |   | 137 |   
|Discontinued operations, net of income taxes |                                          |                         |    |     |      |   |    |      |  |   | 8   |   
|                                             |                                          |                         |     |     |      |   |     |      | 
|Net income                                   |                                          | $                       | 97  |     |      | $ | 99  |      |  | $ | 145 |   
|                                             |                                          |                         |     |     |      |   |     |      | 



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COLORADO INTERSTATE GAS COMPANY




CONSOLIDATED BALANCE SHEETS


(In millions, except share amounts)


|                                       |                                                                                           |                                                         |                                            |     |      |       |       |       |    |       | 
|-------------------------------------- | ----------------------------------------------------------------------------------------- | ------------------------------------------------------- | ------------------------------------------ | --- | ---- | ----- | ----- | ----- | -- | ----- | 
|                                       |                                                                                           | December 31,                                            |                                           
|                                       |                                                                                           |                                                         |                                           
|                                       |                                                                                           | 2005                                                    |                                            |     | 2004 |      
|                                       |                                                                                           |                                                         |                                            |     |      |      
|ASSETS                                
|                                      
|Current assets                         |                                                                                           |                                                         |                                            |     |      |       |       |      
|                                       | Cash and cash equivalents                                                                 |                                                         | $                                          |    |      |       | $     |      |   
|                                       | Accounts and notes receivable                                                             |                                                         |                                            |     |      |       |       |       |   
|                                       |                                                                                           | Customer, net of allowance of $3 in 2005 and $4 in 2004 |                                            |     | 45   |       |       |       | 41 |      
|                                       |                                                                                           | Affiliates                                              |                                            |     | 4    |       |       |       | 45 |      
|                                       |                                                                                           | Other                                                   |                                            |     | 1    |       |       |       | 1  |      
|                                       | Materials and supplies                                                                    |                                                         |                                            | 3   |      |       |       | 3     |   
|                                       | Deferred income taxes                                                                     |                                                         |                                            | 7   |      |       |       | 5     |   
|                                       | Prepaids and other                                                                        |                                                         |                                            | 22  |      |       |       | 4     |   
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                       |                                                                                           |                                                         | Total current assets                       |     |      | 82    |       |       |    | 99    | 
|                                       |                                                                                           |                                                         |                                            |     |      |      
|Property, plant and equipment, at cost |                                                                                           |                                                         | 1,792                                      |     |      |       | 1,655 |      
|                                       | Less accumulated depreciation, depletion and amortization                                 |                                                         |                                            | 547 |      |       |       | 530   |   
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                       |                                                                                           |                                                         | Total property, plant and equipment, net   |     |      | 1,245 |       |       |    | 1,125 | 
|                                       |                                                                                           |                                                         |                                            |     |      |      
|Other assets                           |                                                                                           |                                                         |                                            |     |      |       |       |      
|                                       | Notes receivable from affiliates                                                          |                                                         |                                            | 757 |      |       |       | 538   |   
|                                       | Other                                                                                     |                                                         |                                            | 34  |      |       |       | 27    |   
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                       |                                                                                           |                                                         | 791                                        |     |      |       | 565   |      
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                       |                                                                                           |                                                         | Total assets                               |     | $    | 2,118 |       |       | $  | 1,789 | 
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                      
|LIABILITIES AND STOCKHOLDERS EQUITY  
|Current liabilities                    |                                                                                           |                                                         |                                            |     |      |       |       |      
|                                       | Accounts payable                                                                          |                                                         |                                            |     |      |       |       |       |   
|                                       |                                                                                           | Trade                                                   |                                            | $   | 19   |       |       | $     | 12 |      
|                                       |                                                                                           | Affiliates                                              |                                            |     | 19   |       |       |       | 9  |      
|                                       |                                                                                           | Other                                                   |                                            |     | 22   |       |       |       | 8  |      
|                                       | Current maturities of long-term debt                                                      |                                                         |                                            |    |      |       |       | 192   |   
|                                       | Taxes payable                                                                             |                                                         |                                            | 59  |      |       |       | 57    |   
|                                       | Accrued liabilities                                                                       |                                                         |                                            | 10  |      |       |       | 5     |   
|                                       | Accrued interest                                                                          |                                                         |                                            | 8   |      |       |       | 1     |   
|                                       | Other                                                                                     |                                                         |                                            | 17  |      |       |       | 9     |   
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                       |                                                                                           |                                                         | Total current liabilities                  |     |      | 154   |       |       |    | 293   | 
|                                       |                                                                                           |                                                         |                                            |     |      |      
|Long-term debt                         |                                                                                           |                                                         | 700                                        |     |      |       | 118   |      
|                                       |                                                                                           |                                                         |                                            |     |      |      
|Other liabilities                      |                                                                                           |                                                         |                                            |     |      |       |       |      
|                                       | Deferred income taxes                                                                     |                                                         |                                            | 221 |      |       |       | 215   |   
|                                       | Other                                                                                     |                                                         |                                            | 34  |      |       |       | 36    |   
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                       |                                                                                           |                                                         | 255                                        |     |      |       | 251   |      
|                                       |                                                                                           |                                                         |                                            |     |      |      
|Commitments and contingencies          |                                                                                           |                                                         |                                            |     |      |       |       |      
|                                      
|Stockholders equity                   |                                                                                           |                                                         |                                            |     |      |       |       |      
|                                       | Common stock, par value $1 per share; 1,000 shares
    authorized, issued and outstanding |                                                         |                                            |    |      |       |       |      |   
|                                       | Additional paid-in capital                                                                |                                                         |                                            | 47  |      |       |       | 108   |   
|                                       | Retained earnings                                                                         |                                                         |                                            | 962 |      |       |       | 1,019 |   
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                       |                                                                                           |                                                         | Total stockholders equity                 |     |      | 1,009 |       |       |    | 1,127 | 
|                                       |                                                                                           |                                                         |                                            |     |      |      
|                                       |                                                                                           |                                                         | Total liabilities and stockholders equity |     | $    | 2,118 |       |       | $  | 1,789 | 
|                                       |                                                                                           |                                                         |                                            |     |      |      



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COLORADO INTERSTATE GAS COMPANY


CONSOLIDATED STATEMENTS OF CASH FLOWS


(In millions)


|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |      |     |      |      |      |     |     |  
|---------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------- | --------------------------------- | --------------------------------------------------- | ---- | -- | ---- | ---- | ---- | --- | ---- | ---- | ---- | --- | --- | -
|                                                                       |                                                                                                          | Year Ended December 31,                                       |                                  
|                                                                       |                                                                                                          |                                                               |                                  
|                                                                       |                                                                                                          | 2005                                                          |                                   |                                                     | 2004 |    |      | 2003 |     
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|Cash flows from operating activities                                   |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |      |     |      |     
|                                                                       | Net income                                                                                               |                                                               | $                                 | 97                                                  |      |    | $    | 99   |      |     | $    | 145  |     
|                                                                       |                                                                                                          | Less income from discontinued operations, net of income taxes |                                   |                                                     |     |    |      |      |     |     |      |      | 8    |    
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|                                                                       | Net income from continuing operations                                                                    |                                                               |                                   | 97                                                  |      |    |      | 99   |      |     |      | 137  |     
|                                                                       | Adjustments to reconcile net income from continuing operations
    to net cash from operating activities |                                                               |                                   |                                                     |      |    |      |      |      |     |      |      |     
|                                                                       |                                                                                                          | Depreciation, depletion and amortization                      |                                   |                                                     | 43   |    |      |      | 41   |     |      |      | 34   |    
|                                                                       |                                                                                                          | Deferred income taxes                                         |                                   |                                                     | 4    |    |      |      | 15   |     |      |      | 37   |    
|                                                                       |                                                                                                          | Gain on sale of long-lived assets                             |                                   |                                                     |     |    |      |      |     |     |      |      | (6   | )  
|                                                                       |                                                                                                          | Re-application of SFAS No. 71                                 |                                   |                                                     |     |    |      |      |     |     |      |      | (18  | )  
|                                                                       |                                                                                                          | Other non-cash income items                                   |                                   |                                                     | (5   | )  |      |      | 2    |     |      |      | 6    |    
|                                                                       |                                                                                                          | Asset and liability changes                                   |                                   |                                                     |      |    |      |      |      |     |      |      |      |    
|                                                                       |                                                                                                          |                                                               | Accounts receivable               |                                                     |      | 35 |      |      |      | (9  | )    |      |      | 65  |    
|                                                                       |                                                                                                          |                                                               | Accounts payable                  |                                                     |      | 17 |      |      |      | 19  |      |      |      | (51 | )  
|                                                                       |                                                                                                          |                                                               | Taxes payable                     |                                                     |      |   |      |      |      | (24 | )    |      |      | (13 | )  
|                                                                       |                                                                                                          |                                                               | Other asset and liability changes |                                                     |      |    |      |      |      |     |      |      |      |     |    
|                                                                       |                                                                                                          |                                                               |                                   | Assets                                              |      |    | (11  | )    |      |     | 1    |      |      |     | (17 | )
|                                                                       |                                                                                                          |                                                               |                                   | Liabilities                                         |      |    | 19   |      |      |     | (10  | )    |      |     | (27 | )
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|                                                                       |                                                                                                          | Cash provided by continuing operations                        |                                   |                                                     | 199  |    |      |      | 134  |     |      |      | 147  |    
|                                                                       |                                                                                                          | Cash used in discontinued operations                          |                                   |                                                     |     |    |      |      |     |     |      |      | (4   | )  
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|                                                                       |                                                                                                          |                                                               |                                   | Net cash provided by operating activities           |      |    | 199  |      |      |     | 134  |      |      |     | 143 |  
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|Cash flows from investing activities                                   |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |      |     |      |     
|                                                                       | Additions to property, plant and equipment                                                               |                                                               |                                   | (148                                                | )    |    |      | (61  | )    |     |      | (50  | )   
|                                                                       | Proceeds from the sale of assets and investments                                                         |                                                               |                                   |                                                    |      |    |      | 1    |      |     |      | 9    |     
|                                                                       | Net change in affiliate advances                                                                         |                                                               |                                   | (216                                                | )    |    |      | (63  | )    |     |      | (129 | )   
|                                                                       | Other                                                                                                    |                                                               |                                   |                                                    |      |    |      | (3   | )    |     |      | (1   | )   
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|                                                                       |                                                                                                          | Cash used in continuing operations                            |                                   |                                                     | (364 | )  |      |      | (126 | )   |      |      | (171 | )  
|                                                                       |                                                                                                          | Cash provided by discontinued operations                      |                                   |                                                     |     |    |      |      |     |     |      |      | 74   |    
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|                                                                       |                                                                                                          |                                                               |                                   | Net cash used in investing activities               |      |    | (364 | )    |      |     | (126 | )    |      |     | (97 | )
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|Cash flows from financing activities                                   |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |      |     |      |     
|                                                                       | Net proceeds from issuance of long-term debt                                                             |                                                               |                                   | 590                                                 |      |    |      |     |      |     |      |     |     
|                                                                       | Payments to retire long-term debt                                                                        |                                                               |                                   | (210                                                | )    |    |      | (11  | )    |     |      | (11  | )   
|                                                                       | Dividends paid                                                                                           |                                                               |                                   |                                                    |      |    |      |     |      |     |      | (41  | )   
|                                                                       | Distribution                                                                                             |                                                               |                                   | (215                                                | )    |    |      |     |      |     |      |     |     
|                                                                       | Contributions from discontinued operations                                                               |                                                               |                                   |                                                    |      |    |      |     |      |     |      | 70   |     
|                                                                       | Other                                                                                                    |                                                               |                                   |                                                    |      |    |      | (1   | )    |     |      | (1   | )   
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|                                                                       |                                                                                                          | Cash provided by (used in) continuing operations              |                                   |                                                     | 165  |    |      |      | (12  | )   |      |      | 17   |    
|                                                                       |                                                                                                          | Cash used in discontinued operations                          |                                   |                                                     |     |    |      |      |     |     |      |      | (70  | )  
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|                                                                       |                                                                                                          |                                                               |                                   | Net cash provided by (used in) financing activities |      |    | 165  |      |      |     | (12  | )    |      |     | (53 | )
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|Net change in cash and cash equivalents from continuing
    operations |                                                                                                          |                                                               |                                  |                                                     |      |    | (4   | )    |      |     | (7   | )   
|Cash and cash equivalents                                              |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |      |     |      |     
|                                                                       | Beginning of period                                                                                      |                                                               |                                   |                                                    |      |    |      | 4    |      |     |      | 11   |     
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     
|                                                                       | End of period                                                                                            |                                                               | $                                 |                                                    |      |    | $    |     |      |     | $    | 4    |     
|                                                                       |                                                                                                          |                                                               |                                   |                                                     |      |    |      |      |     



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COLORADO INTERSTATE GAS COMPANY




CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY


(In millions, except share amounts)


|                  |                                               |              |       |            |        |   |          |  |       |               |     |     |        |   |       |      |   |   |       |      |  
|----------------- | --------------------------------------------- | ------------ | ----- | ---------- | ------ | - | -------- |  | ----- | ------------- | --- | --- | ------ | - | ----- | ---- | - | - | ----- | ---- | -
|                  |                                               | Common stock |       | Additional |        |   |          |  | Total |              
|                  |                                               |              |       | paid-in    |        |   | Retained |  |       | stockholders |    
|                  |                                               | Shares       |       |            | Amount |   | capital  |  |       | earnings      |     |     | equity |  
|                  |                                               |              |       |            |        |   |          |  |       |               |     |     |        |  
|January 1, 2003   |                                               |              | 1,000 |            |        | $ |         |  |       | $             | 109 |     |        | $ | 816   |      |   | $ | 925   |     
|                  | Net income                                    |              |       |            |        |   |          |  |       |               |     |     |        |   |       | 145  |   |   |       | 145  |  
|                  | Allocated tax expense of El Paso equity plans |              |       |            |        |   |          |  |       |               |     | (1  | )      |   |       |      |   |   |       | (1   | )
|                  | Dividends                                     |              |       |            |        |   |          |  |       |               |     |     |        |   |       | (41  | ) |   |       | (41  | )
|                  |                                               |              |       |            |        |   |          |  |       |               |     |     |        |   |      
|December 31, 2003 |                                               |              | 1,000 |            |        |   |         |  |       |               | 108 |     |        |   | 920   |      |   |   | 1,028 |     
|                  | Net income                                    |              |       |            |        |   |          |  |       |               |     |     |        |   |       | 99   |   |   |       | 99   |  
|                  |                                               |              |       |            |        |   |          |  |       |               |     |     |        |   |      
|December 31, 2004 |                                               |              | 1,000 |            |        |   |         |  |       |               | 108 |     |        |   | 1,019 |      |   |   | 1,127 |     
|                  | Net income                                    |              |       |            |        |   |          |  |       |               |     |     |        |   |       | 97   |   |   |       | 97   |  
|                  | Distribution                                  |              |       |            |        |   |          |  |       |               |     | (61 | )      |   |       | (154 | ) |   |       | (215 | )
|                  |                                               |              |       |            |        |   |          |  |       |               |     |     |        |   |      
|December 31, 2005 |                                               |              | 1,000 |            |        | $ |         |  |       | $             | 47  |     |        | $ | 962   |      |   | $ | 1,009 |     
|                  |                                               |              |       |            |        |   |          |  |       |               |     |     |        |   |      



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COLORADO INTERSTATE GAS COMPANY


NOTES TO CONSOLIDATED FINANCIAL STATEMENTS


1. Summary of Significant Accounting Policies


Basis of Presentation and Principles of
Consolidation






| |                 
| | ----------------
| | Use of Estimates



Regulated Operations


Accounting for the Effect of Certain Types of
Regulation






| |                          
| | -------------------------
| | Cash and Cash Equivalents



Allowance for Doubtful Accounts




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| |                       
| | ----------------------
| | Materials and Supplies



Natural Gas Imbalances








| |                              
| | -----------------------------
| | Property, Plant and Equipment









FERC-approved


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##### Table of Contents



Asset Impairments






| |                    
| | -------------------
| | Revenue Recognition





| |                                            
| | -------------------------------------------
| | Environmental Costs and Other Contingencies







22



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##### Table of Contents





| |             
| | ------------
| | Income Taxes





Accounting for Asset Retirement Obligations


Accounting for
Asset Retirement Obligations, Accounting for Conditional Asset Retirement
Obligations,




New Accounting Pronouncements Issued But
Not Yet Adopted




Accounting for Pipeline Integrity Costs.


2. Acquisition of Affiliate




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3. Discontinued Operations and Divestitures




| |                        
| | -----------------------
| | Discontinued Operations





|                   |                        |                                                          |   |     |    | 
|------------------ | ---------------------- | -------------------------------------------------------- | - | --- | -- | 
|                   |                        | December 31,                                             |  
|                   |                        | 2003                                                     |  
|                   |                        |                                                          |  
|                   |                        | (In millions)                                            |  
|Operating Results: |                        |                                                          |   |    
|                   | Revenues               |                                                          | $ | 67  |   
|                   | Costs and expenses     |                                                          |   | (67 | ) 
|                   | Gain on sale of assets |                                                          |   | 12  |   
|                   |                        |                                                          |  
|                   |                        | Operating income                                         |   |     | 12 | 
|                   | Income taxes           |                                                          |   | (4  | ) 
|                   |                        |                                                          |  
|                   |                        | Income from discontinued operations, net of income taxes |   | $   | 8  | 
|                   |                        |                                                          |  





| |             
| | ------------
| | Divestitures



24



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##### Table of Contents



4. Income Taxes


Components of Income Taxes.


|         |         |                                               |    |    |      |  |    |      |    |  |    |    |    | 
|-------- | ------- | --------------------------------------------- | -- | -- | ---- |  | -- | ---- | -- |  | -- | -- | -- | 
|         |         | 2005                                          |    |    | 2004 |  |    | 2003 |   
|         |         |                                               |    |    |      |  |    |      |   
|         |         | (In millions)                                 |   
|Current  |         |                                               |    |    |      |  |    |      |    |  |    |   
|         | Federal |                                               | $  | 49 |      |  | $  | 41   |    |  | $  | 42 |   
|         | State   |                                               |    | 2  |      |  |    | (2   | )  |  |    | 4  |   
|         |         |                                               |    |    |      |  |    |      |   
|         |         |                                               | 51 |    |      |  | 39 |      |    |  | 46 |   
|         |         |                                               |    |    |      |  |    |      |   
|Deferred |         |                                               |    |    |      |  |    |      |    |  |    |   
|         | Federal |                                               |    | 3  |      |  |    | 13   |    |  |    | 33 |   
|         | State   |                                               |    | 1  |      |  |    | 2    |    |  |    | 4  |   
|         |         |                                               |    |    |      |  |    |      |   
|         |         |                                               | 4  |    |      |  | 15 |      |    |  | 37 |   
|         |         |                                               |    |    |      |  |    |      |   
|         |         | Total income taxes from continuing operations |    | $  | 55   |  |    | $    | 54 |  |    | $  | 83 | 
|         |         |                                               |    |    |      |  |    |      |   

Effective Tax Rate Reconciliation.


|                                                  |                                                                        |                      |    |    |      |   |    |      |   |   |    |   | 
|------------------------------------------------- | ---------------------------------------------------------------------- | -------------------- | -- | -- | ---- | - | -- | ---- | - | - | -- | - | 
|                                                  |                                                                        | 2005                 |    |    | 2004 |   |    | 2003 |  
|                                                  |                                                                        |                      |    |    |      |   |    |      |  
|                                                  |                                                                        | (In millions, except |   
|                                                  |                                                                        | for rates)           |   
|Income taxes at the statutory federal rate of 35% |                                                                        | $                    | 53 |    |      | $ | 54 |      |   | $ | 77 |  
|Increase (decrease)                               |                                                                        |                      |    |    |      |   |    |      |   |   |    |  
|                                                  | Current year state income taxes, net of federal income tax
    benefit |                      |    | 3  |      |   |    | 3    |   |   |    | 5 | 
|                                                  | State income tax adjustment, net of federal income tax benefit         |                      |    | (1 | )    |   |    | (3   | ) |   |    |  | 
|                                                  | Other                                                                  |                      |    |   |      |   |    |     |   |   |    | 1 | 
|                                                  |                                                                        |                      |    |    |      |   |    |      |  
|Income taxes from continuing operations           |                                                                        | $                    | 55 |    |      | $ | 54 |      |   | $ | 83 |  
|                                                  |                                                                        |                      |    |    |      |   |    |      |  
|Effective tax rate                                |                                                                        |                      | 36 | %  |      |   | 35 | %    |   |   | 38 | %
|                                                  |                                                                        |                      |    |    |      |   |    |      |  

Deferred Tax Assets and Liabilities.


|                           |                               |                              |     |     |      |   |     |     |     | 
|-------------------------- | ----------------------------- | ---------------------------- | --- | --- | ---- | - | --- | --- | --- | 
|                           |                               | 2005                         |     |     | 2004 |  
|                           |                               |                              |     |     |      |  
|                           |                               | (In millions)                |    
|Deferred tax liabilities   |                               |                              |     |     |      |   |     |    
|                           | Property, plant and equipment |                              | $   | 220 |      |   | $   | 209 |    
|                           | Other                         |                              |     | 18  |      |   |     | 16  |    
|                           |                               |                              |     |     |      |  
|                           |                               | Total deferred tax liability |     |     | 238  |   |     |     | 225 | 
|                           |                               |                              |     |     |      |  
|Deferred tax assets        |                               |                              |     |     |      |   |     |    
|                           | Other                         |                              |     | 24  |      |   |     | 15  |    
|                           |                               |                              |     |     |      |  
|                           |                               | Total deferred tax asset     |     |     | 24   |   |     |     | 15  | 
|                           |                               |                              |     |     |      |  
|Net deferred tax liability |                               | $                            | 214 |     |      | $ | 210 |    
|                           |                               |                              |     |     |      |  

Other Tax Matters.


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5. Financial Instruments




|                                     |                                                     |               |   |     |       |  |   |          |  |  |       |     |  |  |   |     | 
|------------------------------------ | --------------------------------------------------- | ------------- | - | --- | ----- |  | - | -------- |  |  | ----- | --- |  |  | - | --- | 
|                                     |                                                     | 2005          |   |     | 2004  | 
|                                     |                                                     |               |   |     |       | 
|                                     |                                                     | Carrying      |   |     | Fair  |  |   | Carrying |  |  | Fair  |    
|                                     |                                                     | Amount        |   |     | Value |  |   | Amount   |  |  | Value |    
|                                     |                                                     |               |   |     |       |  |   |          |  |  |       |    
|                                     |                                                     | (In millions) |  
|Balance sheet financial instruments: |                                                     |               |   |     |       |  |   |          |  |  |       |     |  |  |   |    
|                                     | Long-term debt, including current
    maturities(1) |               | $ | 700 |       |  | $ | 710      |  |  | $     | 310 |  |  | $ | 320 | 




|    |                                                                                                                                
|--- | -------------------------------------------------------------------------------------------------------------------------------
|(1) | We estimated the fair value of debt with fixed interest rates
    based on quoted market prices for the same or similar issues.



6. Regulatory Assets and Liabilities




|                                   |                                                                             |                                     |   |    |      |   |   |    |    | 
|---------------------------------- | --------------------------------------------------------------------------- | ----------------------------------- | - | -- | ---- | - | - | -- | -- | 
|Description                        |                                                                             | 2005                                |   |    | 2004 |  
|                                   |                                                                             |                                     |   |    |      |  
|                                   |                                                                             | (In millions)                       |  
|Current regulatory asset           |                                                                             | $                                   | 2 |    |      | $ |  |   
|Non-current regulatory assets      |                                                                             |                                     |   |    |      |   |   |   
|                                   | Grossed-up deferred taxes on capitalized funds used during
    construction |                                     |   | 14 |      |   |   | 12 |   
|                                   | Postretirement benefits                                                     |                                     |   | 5  |      |   |   | 6  |   
|                                   | Under-collected deferred income taxes                                       |                                     |   | 2  |      |   |   | 2  |   
|                                   |                                                                             |                                     |   |    |      |  
|                                   |                                                                             | Total regulatory
    assets(1)      |   | $  | 23   |   |   | $  | 20 | 
|                                   |                                                                             |                                     |   |    |      |  
|Current regulatory liabilities     |                                                                             | $                                   | 7 |    |      | $ |  |   
|Non-current regulatory liabilities |                                                                             |                                     |   |    |      |   |   |   
|                                   | Excess deferred income taxes                                                |                                     |   | 2  |      |   |   | 3  |   
|                                   | Over-collected fuel variance                                                |                                     |   | 8  |      |   |   | 11 |   
|                                   |                                                                             |                                     |   |    |      |  
|                                   |                                                                             | Total regulatory
    liabilities(1) |   | $  | 17   |   |   | $  | 14 | 
|                                   |                                                                             |                                     |   |    |      |  




|    |                                                                                                                                     
|--- | ------------------------------------------------------------------------------------------------------------------------------------
|(1) | Amounts are included as other current and non-current assets and
    other current and non-current liabilities in our balance sheet.

7. Debt and Credit Facilities


Debt




|                                     |                                               |               |     |     |      |   |     |     | 
|------------------------------------ | --------------------------------------------- | ------------- | --- | --- | ---- | - | --- | --- | 
|                                     |                                               | 2005          |     |     | 2004 |  
|                                     |                                               |               |     |     |      |  
|                                     |                                               | (In millions) |    
|10% Senior Debentures due 2005       |                                               | $             |    |     |      | $ | 180 |    
|Variable Interest Rate Note due 2007 |                                               |               |    |     |      |   | 30  |    
|5.95% Senior Notes due 2015          |                                               |               | 200 |     |      |   |    |    
|6.80% Senior Notes due 2015          |                                               |               | 400 |     |      |   |    |    
|6.85% Senior Debentures due 2037     |                                               |               | 100 |     |      |   | 100 |    
|                                     |                                               |               |     |     |      |  
|                                     |                                               |               | 700 |     |      |   | 310 |    
|Less: current maturities             |                                               |               |    |     |      |   | 192 |    
|                                     |                                               |               |     |     |      |  
|                                     | Total long-term debt, less current maturities |               | $   | 700 |      |   | $   | 118 | 
|                                     |                                               |               |     |     |      |  



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cross-acceleration




Credit Facilities






8. Commitments and Contingencies


Legal Proceedings


Grynberg. In re: Natural Gas Royalties Qui Tam
Litigation


Will Price (formerly Quinque). Will Price,
et al. v. Gas Pipelines and Their Predecessors,
et al.,


27



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| |                      
| | ---------------------
| | Environmental Matters





|                                                 |  |   |    |  
|------------------------------------------------ |  | - | -- | -
|Balance at January 1, 2005                       |  | $ | 14 |  
|Additions/adjustments for remediation activities |  |   | 13 |  
|Payments for remediation activities              |  |   | (4 | )
|                                                 |  |   |   
|Balance at December 31, 2005                     |  | $ | 23 |  
|                                                 |  |   |   







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Capital and Other Commitments




Operating Leases




|             |       |                  |   |   | 
|------------ | ----- | ---------------- | - | - | 
|Year Ending  |       |                 
|December 31, |       | Operating Leases |  
|             |       |                  |  
|             |       | (In millions)    |  
|2006         |       | $                | 2 |  
|2007         |       |                  | 2 |  
|2008         |       |                  | 2 |  
|2009         |       |                  | 2 |  
|             |       |                  |  
|             | Total |                  | $ | 8 | 
|             |       |                  |  



Other Commercial Commitments






| |              
| | -------------
| | Capital Lease





|                                            |  |               |    | 
|------------------------------------------- |  | ------------- | -- | 
|Year Ending                                 |  |              
|December 31,                                |  | (In millions) |   
|                                            |  |               |   
|2006                                        |  | $             | 1  | 
|2007                                        |  |               | 1  | 
|2008                                        |  |               | 1  | 
|2009                                        |  |               | 1  | 
|2010                                        |  |               | 1  | 
|Thereafter                                  |  |               | 15 | 
|                                            |  |               |   
|Total minimum lease payments                |  |               | 20 | 
|                                           
|Less: amount representing interest          |  |               | 11 | 
|                                            |  |               |   
|Present value of net minimum lease payments |  | $             | 9  | 
|                                            |  |               |   

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9. Retirement Benefits


Pension and Retirement Benefits






| |                        
| | -----------------------
| | Postretirement Benefits

co-payment


Accounting and Disclosure Requirements Related to the
Medicare Prescription Drug, Improvement and Modernization Act of
2003




|                                 |                                                      |               |   |    |      |  |   |    |  
|-------------------------------- | ---------------------------------------------------- | ------------- | - | -- | ---- |  | - | -- | -
|                                 |                                                      | 2005          |   |    | 2004 | 
|                                 |                                                      |               |   |    |      | 
|                                 |                                                      | (In millions) |  
|Change in benefit obligation:    |                                                      |               |   |    |      |  |   |   
|                                 | Projected benefit obligation at beginning of period: |               | $ | 12 |      |  | $ | 12 |  
|                                 | Interest cost                                        |               |   |   |      |  |   | 1  |  
|                                 | Participant contributions                            |               |   | 1  |      |  |   | 1  |  
|                                 | Benefits paid                                        |               |   | (2 | )    |  |   | (2 | )
|                                 |                                                      |               |   |    |      | 
|                                 | Projected benefit obligation at end of period        |               | $ | 11 |      |  | $ | 12 |  
|                                 |                                                      |               |   |    |      | 
|Change in plan assets:           |                                                      |               |   |    |      |  |   |   
|                                 | Fair value of plan assets at beginning of period     |               | $ | 14 |      |  | $ | 13 |  
|                                 | Actual return on plan assets                         |               |   | 1  |      |  |   | 1  |  
|                                 | Employer contributions                               |               |   | 2  |      |  |   | 1  |  
|                                 | Participant contributions                            |               |   | 1  |      |  |   | 1  |  
|                                 | Benefits paid                                        |               |   | (2 | )    |  |   | (2 | )
|                                 |                                                      |               |   |    |      | 
|                                 | Fair value of plan assets at end of period           |               | $ | 16 |      |  | $ | 14 |  
|                                 |                                                      |               |   |    |      | 
|Reconciliation of funded status: |                                                      |               |   |    |      |  |   |   
|                                 | Funded status at September 30                        |               | $ | 5  |      |  | $ | 2  |  
|                                 | Unrecognized actuarial gain                          |               |   | (6 | )    |  |   | (5 | )
|                                 |                                                      |               |   |    |      | 
|                                 | Net accrued benefit cost at December 31              |               | $ | (1 | )    |  | $ | (3 | )
|                                 |                                                      |               |   |    |      | 

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|             |       |   |   |    | 
|------------ | ----- | - | - | -- | 
|Year Ending  |       |  
|December 31, |       |  
|             |       |  
|2006         |       | $ | 1 |   
|2007         |       |   | 1 |   
|2008         |       |   | 1 |   
|2009         |       |   | 1 |   
|2010         |       |   | 1 |   
|2011 - 2014  |       |   | 5 |   
|             |       |   |  
|             | Total |   | $ | 10 | 
|             |       |   |  



|                                |  |               |   |      |  |   |      |   |  |   |    |  
|------------------------------- |  | ------------- | - | ---- |  | - | ---- | - |  | - | -- | -
|                                |  | 2005          |   | 2004 |  |   | 2003 |  
|                                |  |               |   |      |  |   |      |  
|                                |  | (In millions) |  
|Interest cost                   |  | $             |  |      |  | $ | 1    |   |  | $ | 1  |  
|Expected return on plan assets  |  |               |  |      |  |   | (1   | ) |  |   | (1 | )
|                                |  |               |   |      |  |   |      |   | 
|Net postretirement benefit cost |  | $             |  |      |  | $ |     |   |  | $ |   |  
|                                |  |               |   |      |  |   |      |   | 



|                                                            |                                       |           |  |      |      |  |  |      |  |  |  |      | 
|----------------------------------------------------------- | ------------------------------------- | --------- |  | ---- | ---- |  |  | ---- |  |  |  | ---- | 
|                                                            |                                       | 2005      |  |      | 2004 |  |  | 2003 | 
|                                                            |                                       |           |  |      |      |  |  |      | 
|                                                            |                                       | (Percent) | 
|Assumptions related to benefit obligations at September 30: |                                       |           |  |      |      |  |  |      |  |  |  |     
|                                                            | Discount rate                         |           |  | 5.25 |      |  |  | 5.75 |  |  |  |      | 
|Assumptions related to benefit costs at December 31:        |                                       |           |  |      |      |  |  |      |  |  |  |     
|                                                            | Discount rate                         |           |  | 5.75 |      |  |  | 6.00 |  |  |  | 6.75 | 
|                                                            | Expected return on plan
    assets(1) |           |  | 7.50 |      |  |  | 7.50 |  |  |  | 7.50 | 






|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|--- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|(1) | The expected return on plan assets is a pre-tax rate (before a
    tax rate ranging from 35 percent to 38 percent on
    postretirement benefits) that is primarily based on an expected
    risk-free investment return, adjusted for historical risk
    premiums and specific risk adjustments associated with our debt
    and equity securities. These expected returns were then weighted
    based on the target asset allocations of our investment
    portfolio.





| |                           
| | --------------------------
| | Postretirement Plan Assets



|                  |       |           |    |     |        |  |    |     | 
|----------------- | ----- | --------- | -- | --- | ------ |  | -- | --- | 
|                  |       | Actual    |    |     | Actual | 
|Asset Category    |       | 2005      |    |     | 2004   | 
|                  |       |           |    |     |        | 
|                  |       | (Percent) |   
|Equity securities |       |           | 59 |     |        |  | 56 |    
|Debt securities   |       |           | 31 |     |        |  | 30 |    
|Other             |       |           | 10 |     |        |  | 14 |    
|                  |       |           |    |     |        | 
|                  | Total |           |    | 100 |        |  |    | 100 | 
|                  |       |           |    |     |        | 

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10. Transactions with Major Customer




|                                   |  |               |    |  |      |   |    |      |  |   |    | 
|---------------------------------- |  | ------------- | -- |  | ---- | - | -- | ---- |  | - | -- | 
|                                   |  | 2005          |    |  | 2004 |   |    | 2003 | 
|                                   |  |               |    |  |      |   |    |      | 
|                                   |  | (In millions) |   
|Public Service Company of Colorado |  | $             | 98 |  |      | $ | 99 |      |  | $ | 98 | 

11. Supplemental Cash Flow Information




|                                           |  |               |    |  |      |  |    |      |  |  |    | 
|------------------------------------------ |  | ------------- | -- |  | ---- |  | -- | ---- |  |  | -- | 
|                                           |  | 2005          |    |  | 2004 |  |    | 2003 | 
|                                           |  |               |    |  |      |  |    |      | 
|                                           |  | (In millions) |   
|Interest paid, net of capitalized interest |  |               | 26 |  |      |  | 28 |      |  |  | 28 | 
|Income tax payments                        |  |               | 51 |  |      |  | 64 |      |  |  | 70 | 

12. Transactions with Affiliates


Cash Management Program.


Taxes.


Other Affiliate Balances.


|                            |  |               |   |  |      |   |   | 
|--------------------------- |  | ------------- | - |  | ---- | - | - | 
|                            |  | 2005          |   |  | 2004 |  
|                            |  |               |   |  |      |  
|                            |  | (In millions) |  
|Non-current note receivable |  | $             | 7 |  |      | $ | 7 | 
|Contractual deposits        |  |               | 5 |  |      |   | 5 | 



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Affiliate Revenues and Expenses.


Share-Based Payment,




|                                                           |  |               |    |  |      |   |    |      |  |   |    | 
|---------------------------------------------------------- |  | ------------- | -- |  | ---- | - | -- | ---- |  | - | -- | 
|                                                           |  | 2005          |    |  | 2004 |   |    | 2003 | 
|                                                           |  |               |    |  |      |   |    |      | 
|                                                           |  | (In millions) |   
|Revenues                                                   |  | $             | 28 |  |      | $ | 37 |      |  | $ | 36 | 
|Operation and maintenance expenses from affiliates         |  |               | 48 |  |      |   | 44 |      |  |   | 54 | 
|Reimbursements of operating expenses charged to affiliates |  |               | 6  |  |      |   |   |      |  |   |   | 



|    |                                                                      
|--- | ---------------------------------------------------------------------
|13. | Supplemental Selected Quarterly Financial Information
    (Unaudited)



|     |                    |                |   |    |         |  |   |              |  |  |             |    |  |       |   |     |  |  |   |     | 
|---- | ------------------ | -------------- | - | -- | ------- |  | - | ------------ |  |  | ----------- | -- |  | ----- | - | --- |  |  | - | --- | 
|     |                    | Quarters Ended |   |    |        
|     |                    |                |   |    |        
|     |                    | March 31       |   |    | June 30 |  |   | September 30 |  |  | December 31 |    |  | Total |  
|     |                    |                |   |    |         |  |   |              |  |  |             |    |  |       |  
|     |                    | (In millions)  |  
|2005 |                    |                |   |    |         |  |   |              |  |  |             |    |  |       |   |     |  |  |   |    
|     | Operating revenues |                | $ | 95 |         |  | $ | 86           |  |  | $           | 85 |  |       | $ | 108 |  |  | $ | 374 | 
|     | Operating income   |                |   | 45 |         |  |   | 36           |  |  |             | 17 |  |       |   | 49  |  |  |   | 147 | 
|     | Net income         |                |   | 27 |         |  |   | 23           |  |  |             | 14 |  |       |   | 33  |  |  |   | 97  | 
|2004 |                    |                |   |    |         |  |   |              |  |  |             |    |  |       |   |     |  |  |   |    
|     | Operating revenues |                | $ | 91 |         |  | $ | 81           |  |  | $           | 80 |  |       | $ | 96  |  |  | $ | 348 | 
|     | Operating income   |                |   | 51 |         |  |   | 35           |  |  |             | 27 |  |       |   | 50  |  |  |   | 163 | 
|     | Net income         |                |   | 30 |         |  |   | 21           |  |  |             | 15 |  |       |   | 33  |  |  |   | 99  | 

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REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM








Accounting for the Effects of Certain Types of
Regulation








34



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##### Table of Contents



SCHEDULE II


COLORADO INTERSTATE GAS COMPANY


VALUATION AND QUALIFYING ACCOUNTS


Years Ended December 31, 2005, 2004 and 2003


(In millions)


|            |                                 |            |   |    |            |  |   |               |   |            |          |    |         |           |   |    |   |  |   |    | 
|----------- | ------------------------------- | ---------- | - | -- | ---------- |  | - | ------------- | - | ---------- | -------- | -- | ------- | --------- | - | -- | - |  | - | -- | 
|            |                                 | Balance at |   |    | Charged to |  |   |               |   | Charged to |          |    | Balance |          
|            |                                 | Beginning  |   |    | Costs and  |  |   |               |   | Other      |          |    | at End  |          
|Description |                                 | of Period  |   |    | Expenses   |  |   | Deductions(1) |   |            | Accounts |    |         | of Period |  
|            |                                 |            |   |    |            |  |   |               |   |            |          |    |         |           |  
|2005        |                                 |            |   |    |            |  |   |               |   |            |          |    |         |           |   |    |   |  |   |   
|            | Environmental Reserves          |            | $ | 14 |            |  | $ | 13            |   |            | $        | (4 | )       |           | $ |   |   |  | $ | 23 | 
|            | Allowance for Doubtful Accounts |            |   | 4  |            |  |   |              |   |            |          |   |         |           |   | (1 | ) |  |   | 3  | 
|2004        |                                 |            |   |    |            |  |   |               |   |            |          |    |         |           |   |    |   |  |   |   
|            | Environmental Reserves          |            | $ | 14 |            |  | $ | 3             |   |            | $        | (3 | )       |           | $ |   |   |  | $ | 14 | 
|            | Allowance for Doubtful Accounts |            |   | 4  |            |  |   |              |   |            |          |   |         |           |   |   |   |  |   | 4  | 
|2003        |                                 |            |   |    |            |  |   |               |   |            |          |    |         |           |   |    |   |  |   |   
|            | Legal Reserves                  |            | $ | 2  |            |  | $ | (2            | ) |            | $        |   |         |           | $ |   |   |  | $ |   | 
|            | Environmental Reserves          |            |   | 13 |            |  |   | 3             |   |            |          | (2 | )       |           |   |   |   |  |   | 14 | 
|            | Allowance for Doubtful Accounts |            |   | 3  |            |  |   | (1            | ) |            |          |   |         |           |   | 2  |   |  |   | 4  | 






|    |                                       
|--- | --------------------------------------
|(1) | These amounts represent cash payments.

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|        |                                                                                         
|------- | ----------------------------------------------------------------------------------------
|ITEM 9. | CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING
    AND FINANCIAL DISCLOSURE








|         |                        
|-------- | -----------------------
|ITEM 9A. | CONTROLS AND PROCEDURES

Evaluation of Disclosure Controls and Procedures






Changes in Internal Control Over Financial Reporting







ITEM 9B. OTHER INFORMATION







PART III


10-K.







|         |                                       
|-------- | --------------------------------------
|ITEM 14. | PRINCIPAL ACCOUNTANT FEES AND SERVICES

Audit Fees




All Other Fees




Policy for Approval of Audit and Non-Audit Fees


pre-approval non-audit


36



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##### Table of Contents






PART IV





ITEM 15. EXHIBITS AND FINANCIAL STATEMENT
SCHEDULES


(a) The following documents are filed as part of this
report:






|                                                                                                                                                                     |  |      |    | 
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------- |  | ---- | -- | 
|                                                                                                                                                                     |  | Page |   
|                                                                                                                                                                     |  |      |   
|Consolidated Statements of Income                                                                                                                                    |  |      | 16 | 
|Consolidated Balance Sheets                                                                                                                                          |  |      | 17 | 
|Consolidated Statements of Cash Flows                                                                                                                                |  |      | 18 | 
|Consolidated Statements of Stockholders Equity                                                                                                                      |  |      | 19 | 
|Notes to Consolidated Financial Statements                                                                                                                           |  |      | 20 | 
|Report of Independent Registered Public Accounting Firm                                                                                                              |  |      | 34 | 
|                                                                                                                                                                    
|2. Financial statement schedules.                                                                                                                                    |  |      |    | 
|Schedule II  Valuation and Qualifying
    Accounts                                                                                                                  |  |      | 35 | 
|All other schedules are omitted because they are not applicable,
    or the required information is disclosed in the financial
    statements or accompanying notes. |  |      |    | 
|                                                                                                                                                                    
|3. Exhibit list                                                                                                                                                      |  |      | 38 | 

37



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COLORADO INTERSTATE GAS COMPANY


EXHIBIT LIST


December 31, 2005




|        |      |    |             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|------- | ---- | -- | ----------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Exhibit |      |    |            
|Number  |      |    | Description
|        |      |    |            
|        | 3.A  |    |             | Amended and Restated Certificate of Incorporation dated as of
    March 7, 2002 (Exhibit 3.A to our 2001 Form 10-K).                                                                                                                                                                                                                                                                                                                                                                                                           
|        | 3.B  |    |             | By-laws dated June 24, 2002. (Exhibit 3.B to our 2002 Form
    10-K)                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|        | 4.A  |    |             | Indenture dated as of June 27, 1997, between Colorado
    Interstate Gas Company and The Bank of New York Trust Company,
    N.A. (successor to Harris Trust and Savings Bank), as Trustee
    (Exhibit 4.A to our 2004 Form 10-K).                                                                                                                                                                                                                                                                                            
|        | 4.A  | .1 |             | First Supplemental Indenture dated as of June 27, 1997,
    between Colorado Interstate Gas Company and The Bank of New York
    Trust Company, N.A. (successor to Harris Trust and Savings
    Bank), as Trustee (Exhibit 4.A.1 to our 2004 Form 10-K).                                                                                                                                                                                                                                                                       
|        | 4.A  | .2 |             | Second Supplemental Indenture dated as of March 9, 2005
    between Colorado Interstate Gas Company and The Bank of New York
    Trust Company, N.A., as Trustee (Exhibit 4.A to our
    Form 8-K filed March 14, 2005).                                                                                                                                                                                                                                                                                                       
|        | 4.A  | .3 |             | Third Supplemental Indenture dated as of November 1, 2005
    between Colorado Interstate Gas Company and The Bank of New York
    Trust Company, N.A., as trustee (Exhibit 4.A to our
    Form 8-K filed on November 2, 2005).                                                                                                                                                                                                                                                                                                
|        | 10.A |    |             | Amended and Restated Credit Agreement dated as of
    November 23, 2004, among El Paso Corporation, ANR
    Pipeline Company, Colorado Interstate Gas Company, El Paso
    Natural Gas Company, Tennessee Gas Pipeline Company, the several
    banks and other financial institutions from time to time parties
    thereto and JPMorgan Chase Bank, N.A., as administrative agent
    and as collateral agent (Exhibit 10.A to our Form 8-K
    filed November 29, 2004).                                                    
|        | 10.B |    |             | Amended and Restated Security Agreement dated as of
    November 23, 2004, among El Paso Corporation, ANR
    Pipeline Company, Colorado Interstate Gas Company, El Paso
    Natural Gas Company, Tennessee Gas Pipeline Company, the
    Subsidiary Grantors and certain other credit parties thereto and
    JPMorgan Chase Bank, N.A., not in its individual capacity, but
    solely as collateral agent for the Secured Parties and as the
    depository bank (Exhibit 10.B to our Form 8-K filed
    November 29, 2004).
|        | 10.C |    |             | Registration Rights Agreement dated as of March 9, 2005
    between Colorado Interstate Gas Company and Citigroup Global
    Markets Inc., Credit Suisse First Boston LLC, BNP Paribas
    Securities Corp., Fortis Securities LLC, Greenwich Capital
    Markets, Inc. and Scotia Capital (USA) Inc. (Exhibit 10.A
    to our Form 8-K filed March 14, 2005).                                                                                                                                                                 
|        | 10.D |    |             | No-Notice Storage and Transportation Delivery Service Agreement
    Rate Schedule NNT-1, dated October 1, 2001, between
    Colorado Interstate Gas Company and Public Service Company of
    Colorado (Exhibit 10.G to our 2005 First Quarter Form 10-Q).                                                                                                                                                                                                                                                                     
|        | 10.E |    |             | Registration Rights Agreement, dated as of November 1,
    2005, among Colorado Interstate Gas Company and Citigroup Global
    Markets Inc., Credit Suisse First Boston LLC, ABN AMRO
    Incorporated, BNP Paribas, Greenwich Capital Markets, Inc., HVB
    Capital Markets, Inc., and SG Americas Securities, LLC
    (Exhibit 10.A to our Form 8-K filed on
    November 2, 2005).                                                                                                                                        
|        | 10.F |    |             | Purchase and Sale Agreement, By and Among CIG Gas Supply
    Company, Wyoming Gas Supply Inc., WIC Holdings Inc., El Paso
    Wyoming Gas Supply Company and Wyoming Interstate Company, Ltd.,
    dated November 1, 2005 (Exhibit 10.B to our
    Form 8-K filed on November 2, 2005).                                                                                                                                                                                                                                        
|        | 21   |    |             | Omitted pursuant to the reduced disclosure format permitted by
    General Instruction I to Form 10-K.                                                                                                                                                                                                                                                                                                                                                                                                                         

38



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##### Table of Contents



|        |       |  |             |                                                                                                        
|------- | ----- |  | ----------- | -------------------------------------------------------------------------------------------------------
|Exhibit |       |  |            
|Number  |       |  | Description
|        |       |  |            
|        | *31.A |  |             | Certification of Chief Executive Officer pursuant to Section 302
    of the Sarbanes-Oxley Act of 2002.
|        | *31.B |  |             | Certification of Chief Financial Officer pursuant to Section 302
    of the Sarbanes-Oxley Act of 2002.
|        | *32.A |  |             | Certification of Chief Executive Officer pursuant to Section 906
    of the Sarbanes-Oxley Act of 2002.
|        | *32.B |  |             | Certification of Chief Financial Officer pursuant to Section 906
    of the Sarbanes-Oxley Act of 2002.

Undertaking




39



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##### Table of Contents






SIGNATURES






| |                                
| | -------------------------------
| | COLORADO INTERSTATE GAS COMPANY



| |     |                    
| | --- | -------------------
| | By: | /s/ James J. Cleary

| |                                    
| | -----------------------------------
| |                                    
| | James J. Cleary                    
| | Chairman of the Board and President



|                                     |  |                                                                                                                        |  |               |  | 
|------------------------------------ |  | ---------------------------------------------------------------------------------------------------------------------- |  | ------------- |  | 
|Signature                            |  | Title                                                                                                                  |  | Date         
|                                     |  |                                                                                                                        |  |              
|                                    
|/s/ James J. ClearyJames J. Cleary   |  | Chairman of the Board and President
    (Principal Executive Officer)                                                  |  | March 3, 2006
|                                    
|/s/ John R. SultJohn R. Sult         |  | Senior Vice President,
    Chief Financial Officer and Controller
    (Principal Accounting and
    Financial Officer) |  | March 3, 2006
|                                    
|/s/ Daniel B. MartinDaniel B. Martin |  | Senior Vice President and Director                                                                                     |  | March 3, 2006
|                                    
|/s/ Thomas L. PriceThomas L. Price   |  | Vice President and Director                                                                                            |  | March 3, 2006

40



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##### Table of Contents



COLORADO INTERSTATE GAS COMPANY


EXHIBIT INDEX


December 31, 2005




|        |      |    |             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|------- | ---- | -- | ----------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|Exhibit |      |    |            
|Number  |      |    | Description
|        |      |    |            
|        | 3.A  |    |             | Amended and Restated Certificate of Incorporation dated as of
    March 7, 2002 (Exhibit 3.A to our 2001 Form 10-K).                                                                                                                                                                                                                                                                                                                                                                                                           
|        | 3.B  |    |             | By-laws dated June 24, 2002. (Exhibit 3.B to our 2002 Form
    10-K)                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|        | 4.A  |    |             | Indenture dated as of June 27, 1997, between Colorado
    Interstate Gas Company and The Bank of New York Trust Company,
    N.A. (successor to Harris Trust and Savings Bank), as Trustee
    (Exhibit 4.A to our 2004 Form 10-K).                                                                                                                                                                                                                                                                                            
|        | 4.A  | .1 |             | First Supplemental Indenture dated as of June 27, 1997,
    between Colorado Interstate Gas Company and The Bank of New York
    Trust Company, N.A. (successor to Harris Trust and Savings
    Bank), as Trustee (Exhibit 4.A.1 to our 2004 Form 10-K).                                                                                                                                                                                                                                                                       
|        | 4.A  | .2 |             | Second Supplemental Indenture dated as of March 9, 2005
    between Colorado Interstate Gas Company and The Bank of New York
    Trust Company, N.A., as Trustee (Exhibit 4.A to our
    Form 8-K filed March 14, 2005).                                                                                                                                                                                                                                                                                                       
|        | 4.A  | .3 |             | Third Supplemental Indenture dated as of November 1, 2005
    between Colorado Interstate Gas Company and The Bank of New York
    Trust Company, N.A., as trustee (Exhibit 4.A to our
    Form 8-K filed on November 2, 2005).                                                                                                                                                                                                                                                                                                
|        | 10.A |    |             | Amended and Restated Credit Agreement dated as of
    November 23, 2004, among El Paso Corporation, ANR
    Pipeline Company, Colorado Interstate Gas Company, El Paso
    Natural Gas Company, Tennessee Gas Pipeline Company, the several
    banks and other financial institutions from time to time parties
    thereto and JPMorgan Chase Bank, N.A., as administrative agent
    and as collateral agent (Exhibit 10.A to our Form 8-K
    filed November 29, 2004).                                                    
|        | 10.B |    |             | Amended and Restated Security Agreement dated as of
    November 23, 2004, among El Paso Corporation, ANR
    Pipeline Company, Colorado Interstate Gas Company, El Paso
    Natural Gas Company, Tennessee Gas Pipeline Company, the
    Subsidiary Grantors and certain other credit parties thereto and
    JPMorgan Chase Bank, N.A., not in its individual capacity, but
    solely as collateral agent for the Secured Parties and as the
    depository bank (Exhibit 10.B to our Form 8-K filed
    November 29, 2004).
|        | 10.C |    |             | Registration Rights Agreement dated as of March 9, 2005
    between Colorado Interstate Gas Company and Citigroup Global
    Markets Inc., Credit Suisse First Boston LLC, BNP Paribas
    Securities Corp., Fortis Securities LLC, Greenwich Capital
    Markets, Inc. and Scotia Capital (USA) Inc. (Exhibit 10.A
    to our Form 8-K filed March 14, 2005).                                                                                                                                                                 
|        | 10.D |    |             | No-Notice Storage and Transportation Delivery Service Agreement
    Rate Schedule NNT-1, dated October 1, 2001, between
    Colorado Interstate Gas Company and Public Service Company of
    Colorado (Exhibit 10.G to our 2005 First Quarter Form 10-Q).                                                                                                                                                                                                                                                                     
|        | 10.E |    |             | Registration Rights Agreement, dated as of November 1,
    2005, among Colorado Interstate Gas Company and Citigroup Global
    Markets Inc., Credit Suisse First Boston LLC, ABN AMRO
    Incorporated, BNP Paribas, Greenwich Capital Markets, Inc., HVB
    Capital Markets, Inc., and SG Americas Securities, LLC
    (Exhibit 10.A to our Form 8-K filed on
    November 2, 2005).                                                                                                                                        
|        | 10.F |    |             | Purchase and Sale Agreement, By and Among CIG Gas Supply
    Company, Wyoming Gas Supply Inc., WIC Holdings Inc., El Paso
    Wyoming Gas Supply Company and Wyoming Interstate Company, Ltd.,
    dated November 1, 2005 (Exhibit 10.B to our
    Form 8-K filed on November 2, 2005).                                                                                                                                                                                                                                        



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##### Table of Contents



|        |       |  |             |                                                                                                        
|------- | ----- |  | ----------- | -------------------------------------------------------------------------------------------------------
|Exhibit |       |  |            
|Number  |       |  | Description
|        |       |  |            
|        | 21    |  |             | Omitted pursuant to the reduced disclosure format permitted by
    General Instruction I to Form 10-K. 
|        | *31.A |  |             | Certification of Chief Executive Officer pursuant to Section 302
    of the Sarbanes-Oxley Act of 2002.
|        | *31.B |  |             | Certification of Chief Financial Officer pursuant to Section 302
    of the Sarbanes-Oxley Act of 2002.
|        | *32.A |  |             | Certification of Chief Executive Officer pursuant to Section 906
    of the Sarbanes-Oxley Act of 2002.
|        | *32.B |  |             | Certification of Chief Financial Officer pursuant to Section 906
    of the Sarbanes-Oxley Act of 2002.