# U.S. Securities and
Exchange Commission

# Washington, D.C. 20549

# Form 10-QSB

(Mark One)

[ X ]           
   QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THESECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended September 30, 2004

[    ]        
       TRANSITION REPORT UNDER SECTION 13 OR 15(d) OF THESECURITIES EXCHANGE ACT OF 1934 [No Fee Required]

For the transition
period from _______ to _______

Commission file number
333-105811

Atlas America Public
#122003 Limited Partnership(Name of small business issuer in its charter)

Delaware    
                 
                  
                 
                 
                 
                 
                
                  
 54-2113989
(State or other jurisdiction of            
                 
                 
                 
                 
                 
                (I.R.S. Employer
incorporation or organization)            
                 
                 
                  
                 
                 
          Identification No.)

311 Rouser Road
Moon Township, PA   
                 
                 
                 
                 
                 
                 
                 
                15108
(Address of principal executive offices)          
                 
                 
                 
                 
                 
          (Zip code)

Issuer's telephone number, including area
code: (412) 262-2830

Check
whether the issuer (1) filed all reports required to be filed by Section 13 or 15(d) of
the Exchange Act during the past 12 months (or for such shorter period that the registrant
was required to file such reports), and (2) has been subject to such filing requirements
for the past 90 days. YesX     No

---

# ATLAS AMERICA PUBLIC
#12-2003 Limited Partnership(A Delaware Limited
Partnership)INDEX TO QUARTERLY
REPORTON FORM 10QSB

|         |  | 
|-------- |  | 
|PART I   |  | 
|        
|Item 1.  |  | 
|        
|         |  | 
|        
|         |  | 
|        
|         |  | 
|        
|         |  | 
|        
|         |  | 
|        
|Item 2.  |  | 
|         |  | 
|        
|Item 3.  |  | 
|        
|PART II. |  | 
|        
|Item 6.  |  | 

|SIGNATURES |  |  |  |  |  |  |  | 11
|---------- |  |  |  |  |  |  |  | --

|
|

|CERTIFICATIONS |  |  |  |  |  |  |  | 13-16
|-------------- |  |  |  |  |  |  |  | -----

---

# PART I

# ITEM 1. FINANCIAL
STATEMENTS

# ATLAS AMERICA PUBLIC
#12-2003 Limited Partnership

# (A Delaware Limited
Partnership)BALANCE SHEETS

|                                            | September 30, | December 31,
|------------------------------------------- | ------------- | ------------
|
|                                            |               |             
|
|ASSETS                                      |               |             
|Current Assets:                             |               |             
|Cash                                        |               |             
|Accounts receivable - affiliate             |               |             
|                                            |               |             
|Total current assets                        |               |             
|                                           
|Oil and gas properties (successful efforts) |               |             
|Less accumulated depletion and depreciation |               |             
|                                            |               |             
|                                            |               |             
|                                            |               |             
|                                            |               |             
|                                            |               |             
|                                           
|LIABILITIES AND PARTNERS' CAPITAL           |               |             
|Current liabilities:                        |               |             
|Accrued liabilities                         |               |             
|                                            |               |             
|Total current liabilities                   |               |             
|                                           
|Asset retirement obligations                |               |             
|                                           
|Partners' capital:                          |               |             
|Managing General Partner                    |               |             
|Limited Partners (4,024.015 units)          |               |             
|                                            |               |             
|                                            |               |             
|                                            |               |             
|                                            |               |             
|                                            |               |             

The accompanying notes are an integral part of these financial statements

---

# ATLAS AMERICA PUBLIC
#12-2003 Limited Partnership(A Delaware Limited
Partnership)STATEMENTS OF
OPERATIONS(Unaudited)

|                                          | Three Months Ended | Nine Months Ended
|----------------------------------------- | ------------------ | -----------------
|
|
|                                          |                    |                  
|REVENUES:                                 |                    |                  
|Natural gas and oil sales                 |                    |                  
|Interest income                           |                    |                  
|                                          |                    |                  
|                                          |                    |                  
|Total revenues                            |                    |                  
|                                         
|COSTS AND EXPENSES:                       |                    |                  
|Production expenses                       |                    |                  
|Depletion and depreciation of oil and gas |                    |                  
|properties                                |                    |                  
|Accretion of asset retirement obligation  |                    |                  
|General and administrative expenses       |                    |                  
|                                          |                    |                  
|                                          |                    |                  
|Total expenses                            |                    |                  
|                                          |                    |                  
|                                          |                    |                  
|Net Income                                |                    |                  
|                                          |                    |                  
|                                          |                    |                  
|                                         
|Allocation of net income:                 |                    |                  
|Managing general partner                  |                    |                  
|Limited partners                          |                    |                  
|                                         
|Net income per limited partnership unit:  |                    |                  
|Net income per limited partnership unit   |                    |                  
|                                         
|                                         

The accompanying notes are an integral part of these financial statements

---

# ATLAS AMERICA PUBLIC
#12-2003 Limited Partnership(A Delaware Limited
Partnership)STATEMENTS OF
PARTNERS CAPITAL ACCOUNTSFOR NINE MONTHS ENDED
SEPTEMBER 30, 2004(Unaudited)

|                                                | Managing |  |  
|----------------------------------------------- | -------- |  | -
|
|
|                                                |          |  |  
|Balance at January 1, 2004                      |          |  | $
|Participation in revenue and cost and expenses: |          | 
|Net production revenues                         |          |  |  
|Interest income                                 |          |  |  
|Depletion and depreciation                      |          |  |  
|Accretion of asset retirement obligations       |          |  |  
|General and administrative                      |          |  |  
|                                                |          |  |  
|                                                |          |  |  
|Net income                                      |          |  |  
|                                               
|Contributions                                   |          |  |  
|                                               
|Distributions                                   |          |  |  
|                                                |          |  |  
|                                                |          |  |  
|Balance at September 30, 2004                   |          |  | $
|                                                |          |  |  
|                                               
|                                               
|                                               

The accompanying notes are an integral part of these financial statements

---

# ATLAS AMERICA PUBLIC
#12-2003 Limited Partnership(A Delaware Limited
Partnership)STATEMENT OF CASH FLOWS(Unaudited)

|                                                                                  | Nine Months Ended
|--------------------------------------------------------------------------------- | -----------------
|
|
|                                                                                  |                  
|Cash flows from operating activities:                                             |                  
|Net income                                                                        |                  
|Adjustments to reconcile net income to net cash provided by operating activities: |                  
|Depletion and depreciation                                                        |                  
|Accretion of asset retirement obligations                                         |                  
|Increase in accounts receivable - affiliate                                       |                  
|Increase in accrued liabilities                                                   |                  
|                                                                                 
|                                                                                  |                  
|                                                                                  |                  
|Net cash provided by operating activities                                         |                  
|                                                                                 
|Cash flows from investing activities:                                             |                  
|Capital expenditures                                                              |                  
|                                                                                 
|                                                                                  |                  
|                                                                                  |                  
|Net cash used in investing activities                                             |                  
|                                                                                  |                  
|Cash flows from financing activities:                                             |                  
|Limited partner contributions                                                     |                  
|Distributions to partners                                                         |                  
|                                                                                 
|                                                                                  |                  
|                                                                                  |                  
|Net cash used in financing activities                                             |                  
|                                                                                  |                  
|                                                                                  |                  
|                                                                                 
|Net increase in cash                                                              |                  
|Cash at beginning of period                                                       |                  
|                                                                                  |                  
|                                                                                  |                  
|Cash at end of period                                                             |                  
|                                                                                  |                  
|                                                                                  |                  
|                                                                                 
|Supplemental Schedule of Non-cash Activities:                                     |                  
|Tangible equipment costs contributed by the Managing General Partner              |                  
|                                                                                  |                  
|                                                                                  |                  
|Asset retirement obligations                                                      |                  
|                                                                                  |                  
|                                                                                 
|                                                                                 
|                                                                                 

The accompanying notes are an integral part of these financial statements

---

# ATLAS AMERICA PUBLIC
#12-2003 Limited Partnership(A Delaware Limited
Partnership)NOTES TO FINANCIAL
STATEMENTSSeptember 30, 2004

# NOTE 1  BASIS OF PRESENTATION

The
financial statements of Atlas America Public #12-2003 Limited Partnership (the
Partnership) as of September 30, 2004 and for the three months and nine months ended
September 30, 2004 are unaudited. Certain information and footnote disclosures normally
included in financial statements prepared in accordance with accounting principles
generally accepted in the United States of America have been condensed or omitted in this
Form 10-QSB pursuant to the rules and regulations of the Securities and Exchange
Commission. However, in the opinion of management, these interim financial statements
include all the necessary adjustments to fairly present the results of the interim periods
presented. The unaudited interim financial statements should be read in conjunction with
the audited financial statements included in the Partnerships Form 10-KSB for the
year ended December 31, 2003. The results of operations for the nine months ended
September 30, 2004 may not necessarily be indicative of the results of operations for the
year ending December 31, 2004. The partnership commenced operations in the fourth quarter
of 2003.

# NOTE 2  SUMMARY OF
SIGNIFICANT ACCOUNTING POLICIES

# Fair Value of Financial
Instruments

For
cash and cash equivalents, receivables and payables, the carrying amounts approximate fair
value because of the short maturity of these instruments.

# Asset Retirement
Obligations-Change in Accounting Principle

The
Partnership accounts for the estimated plugging and abandonment costs of the oil and gas
properties in accordance with Statement of Financial Accounting Standards
(SFAS) 143, Accounting for Asset Retirement Obligations.

A
reconciliation of the Partnerships liability for plugging and abandonment costs for
the nine months ending September 30, 2004, is as follows:

|Asset retirement obligations at December 31, 2003  |  |  | $ | --        | 
|-------------------------------------------------- |  |  | - | --------- | 
|Liabilities incurred from drilling wells           |  |  |   | 1,000,000 | 
|Accretion expense                                  |  |  |   | 45,000    | 
|                                                   |  | 
|                                                   | 
|Asset retirement obligations at September 30, 2004 |  |  | $ | 1,045,000 | 
|                                                   |  | 
|                                                  
|                                                  
|                                                  

---

# ATLAS AMERICA PUBLIC
#12-2003 Limited Partnership(A Delaware Limited
Partnership)NOTES TO FINANCIAL
STATEMENTS (Unaudited)September 30, 2004

# NOTE 2  SUMMARY OF
SIGNIFICANT ACCOUNTING POLICIES  (Continued)

# Supplemental Cash Flow
Information

The
Partnership considers temporary investments with a maturity at the date of acquisition of
90 days or less to be cash equivalents. No cash was paid for interest or income taxes for
the nine months ended September 30, 2004.

# Comprehensive Income

The
Partnership is subject to the provisions of SFAS 130, Reporting Comprehensive
Income, which requires disclosure of comprehensive income and its components.
Comprehensive income includes net income and all other changes in equity of a business
during a period from non-owner sources. These changes, other than net income, are referred
to as other comprehensive income. The Partnership has no material elements of
comprehensive income, other than net income, to report.

# NOTE 3 
TRANSACTIONS WITH ATLAS RESOURCES, INC. AND ITS AFFILIATES

The Partnership has entered
into the following significant transactions with Atlas Resources, Inc. ("Atlas"), the Managing General Partner, and its affiliates as provided
under the Partnership agreement:

| |  |  |  |  |  | Administrative  costs which is included in general and administrative costs in the Statement of Operations
are payable to Atlas at $75 per well per month.  Administrative  costs  incurred  for the three and nine
months ended September 30, 2004 were $39,500 and $72,600, respectively.
| |  |  |  | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  |  |  |  | Monthly well  supervision  fees which is included in production expenses in the Statement of Operations
are payable to Atlas at $275 per well per month for operating and maintaining the wells.  Well
supervision  fees  incurred  for the three and nine months  ended  September  30,  2004 were  $137,000  and  $241,000,
respectively.
| |  |  |  | - |  | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  |  |  |  | Transportation  fees which is included in production expenses in the Statement of Operations
are payable to Atlas which range from $.29-$.35 per mcf.  Transportation  costs incurred for the three and nine months
ended September 30, 2004 were $218,800 and $351,800, respectively.
| |  |  |  | - |  | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| |  |  |  |  |  | As managing  general  partner,  Atlas performs all  administrative  and  management  functions for the  Partnership  including
billing  revenues  and paying  expenses.  Accounts  receivable - affiliate on the balance  sheet  represents  the net
production revenues due from Atlas.
| |  |  |  | - |  | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

---

# ITEM 2.
MANAGEMENTS DISCUSSION AND ANALYSIS AND RESULTS OF OPERATIONS (UNAUDITED)

# Forward-Looking
Statements

WHEN
USED IN THIS FORM 10-QSB, THE WORDS BELIEVES ANTICIPATES
EXPECTS AND SIMILAR EXPRESSIONS ARE INTENDED TO IDENTIFY FORWARD-LOOKING
STATEMENTS. SUCH STATEMENTS ARE SUBJECT TO CERTAIN RISKS AND UNCERTAINTIES MORE
PARTICULARLY DESCRIBED IN ITEM 1 OF OUR ANNUAL REPORT ON FORM 10-KSB. THESE RISKS AND
UNCERTAINTIES COULD CAUSE ACTUAL RESULTS TO DIFFER MATERIALLY. READERS ARE CAUTIONED NOT
TO PLACE UNDUE RELIANCE ON THESE FORWARD-LOOKING STATEMENTS, WHICH SPEAK ONLY AS OF THE
DATE HEREOF. WE UNDERTAKE NO OBLIGATION TO PUBLICLY RELEASE THE RESULTS OF ANY REVISIONS
TO FORWARD-LOOKING STATEMENTS WHICH WE MAY MAKE TO REFLECT EVENTS OR CIRCUMSTANCES AFTER
THE DATE OF THIS FORM 10-QSB OR TO REFLECT THE OCCURRENCE OF UNANTICIPATED EVENTS.

The
plan of operations and liquidity discussion should be read in conjunction with our
Financial Statements and the Notes to our Financial Statements.

Our  producing  operations  commenced in the fourth  quarter of 2003. We expect all of our wells to be connected and producing
by the end of our  fourth  quarter  of 2004.  Our wells are  drilled  primarily  in  western  Pennsylvania.  Funds  contributed  by our
investor partners and our managing general partner after our formation are the only funds available to us for drilling  activities,  no
other wells will be drilled  after this initial  group.  At September  30, 2004,  we had  connected 194 gross wells and plugged 6 gross
wells which we determined  were  uneconomic to produce.  The remaining wells are expected to be online by the end of our fourth quarter
ending December 31, 2004.

Results of Operations

The following table sets forth information  relating to revenues recognized and costs and expenses incurred,  daily production
volumes, average sales prices and production cost per equivalent unit during the periods indicated:

|                                                   | Three Months Ended | Nine Months Ended
|-------------------------------------------------- | ------------------ | -----------------
|
|                                                   |                    |                  
|
|                                                   |                    |                  
|Production revenues (in thousands)                 |                    |                  
|Gas                                                |                    |                  
|Oil                                                |                    |                  
|Production  volumes:                               |                    |                  
|Gas (thousands
         of cubic feet (mcf)/day) |                    |                  
|Oil (barrels (bbls)/day)                         |                    |                  
|Average sales prices:                              |                    |                  
|Gas (per mcf)(1)                                   |                    |                  
|Oil (per bbl)                                      |                    |                  
|Average production costs:                          |                    |                  
|As a percent of sales                              |                    |                  
|(per mcf equivalent unit)                          |                    |                  

---

# Critical Accounting
Policies

The
discussion and analysis of our financial condition and results of operations are based
upon our financial statements, which have been prepared in accordance with accounting
principles generally accepted in the United States of America. The preparation of these
financial statements requires us to make estimates and judgments that affect the reported
amounts of our assets, liabilities, revenues and cost and expenses, and related disclosure
of contingent assets and liabilities. On an on-going basis, we evaluate our estimates,
including those related to provision for possible losses, asset retirement obligations, depletion and
certain accrued liabilities. We base our estimates on historical experience and on various
other assumptions that we believe reasonable under the circumstances, the results of which
form the basis for making judgments about the carrying values of assets and liabilities
that are not readily apparent from other sources. Actual results may differ from these
estimates under different assumptions or conditions.

SFAS
No. 143, Accounting for Asset Retirement Obligations (SFAS 143)
establishes requirements for accounting for the removal costs associated with asset
retirements. SFAS 143 resulted in the recording of our estimated future well plugging costs
as an increase to oil and gas properties and an associated asset retirement obligation
liability, which will be accreted over the estimated life of our wells. Depreciation and
depletion will not increase due to adoption as the additional cost basis associated with
the plugging liability was offset by the estimated salvage value to be realized upon
disposal of our wells.

For
a detailed discussion on the application of our remaining policies critical to our
business operations and other accounting policies, see Note 2 of the Notes to
Financial Statements in our Annual Report on Form 10-KSB.

# ITEM 3. CONTROLS AND
PROCEDURES

Evaluation
of Disclosure Controls and Procedures

Our
Managing General Partners Chief Executive Officer and Chief Financial Officer have
evaluated our disclosure controls and procedures, (as defined in Rules 13a-14 and
15d-14 under the Securities Exchange Act of 1923) as of September 30, 2004. Based upon
this evaluation, these officers believe that our disclosure controls and procedures are
effective in ensuring that all material information required to be filed in this quarterly report has been made
known to them in a timely fashion.  There have been no significant changes in internal controls, or in factors that
could significantly affect internal controls, subsequent to the date the Chief Executive Officer and
Chief Financial Officer completed their evaluation.

# PART II. OTHER
INFORMATION

# ITEM 6. Exhibits and
Reports on Form 8-K

We
have not filed any reports on Form 8-K during the period covered by
this report.

---

# SIGNATURES

Pursuant
to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused
this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Atlas America Public #122003 Limited Partnership

By: (Signature and
Title):           Atlas Resources, Inc., Managing General Partner

By: (Signature and Title):      
    /s/ Freddie M. KotekFreddie M. Kotek,
Chairman of the Board of Directors,Chief Executive
Officer and President

Date:  November 15, 2004



In
accordance with the Exchange Act, this report has been signed by the following persons on
behalf of the registrant and in the capacities and on the dates indicated.

By: (Signature and Title):      
    /s/ Freddie M. KotekFreddie M. Kotek,
Chairman of the Board of Directors,Chief Executive
Officer and President

Date:  November 15, 2004



By: (Signature and Title):      
    /s/ Nancy J. McGurkNancy J. McGurk,
Senior Vice-President,Chief Financial
Officer and Chief Accounting Officer

Date:  November 15, 2004

---

# EXHIBIT INDEX

|     | Description                                                          | Location                
|---- | -------------------------------------------------------------------- | ------------------------
|    
|4(a) | Certificate of
                   Limited Partnership for            | Previously filed in Form
|     | Atlas America Public
                   #122003 Limited Partnership | S-1 on June 3,2003      

|4(b) | Amended and Restated
                   Certificate and Agreement           | Previously filed in
                   Form
|---- | --------------------------------------------------------------------------- | -------------------------------------------
|     | of Limited Partnership
                   for Atlas America Public #122003 | S-1 on June 3, 2003                        
|     | Limited Partnership                                                         |                                            

|10(a) | Drilling and
                   Operating Agreement with exhibits | Previously filed in
                   Form
|----- | ----------------------------------------------------------------- | -------------------------------------------
|      |                                                                   | S-1 on June 3, 2003                        



|
|
|
|

|     | 
|---- | 
|31.1 | 
|    
|31.2 | 
|    
|32.1 | 
|     | 
|    
|32.2 | 
|     | 

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