<PAGE>   1

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------

                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                             ---------------------

                                   FORM 10-Q

(Mark One)
[X]             QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

               FOR THE QUARTERLY PERIOD ENDED SEPTEMBER 30, 1999

                                       OR

[ ]             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 1-4101

                             ---------------------

                         TENNESSEE GAS PIPELINE COMPANY
             (Exact Name of Registrant as Specified in its Charter)

<TABLE>
<S>                                            <C>
                   DELAWARE                                      74-1056569
         (State or Other Jurisdiction                         (I.R.S. Employer
      of Incorporation or Organization)                     Identification No.)

           EL PASO ENERGY BUILDING
            1001 LOUISIANA STREET
                HOUSTON, TEXAS                                     77002
   (Address of Principal Executive Offices)                      (Zip Code)
</TABLE>

       Registrant's Telephone Number, Including Area Code: (713) 420-2131

     Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 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.  Yes [X] No [ ]

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

     Common Stock, par value $5 per share. Shares outstanding on November 12,
1999: 208

     TENNESSEE GAS PIPELINE COMPANY MEETS THE CONDITIONS OF GENERAL INSTRUCTION
H(1)(a) AND (b) OF FORM 10-Q AND IS THEREFORE FILING THIS REPORT WITH A REDUCED
DISCLOSURE FORMAT AS PERMITTED BY SUCH INSTRUCTION.

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
<PAGE>   2

                                    GLOSSARY

     The following abbreviations, acronyms, or defined terms used in this Form
10-Q are defined below:

<TABLE>
<CAPTION>
                                       DEFINITIONS
                                       -----------
<S>                           <C>
ALJ.........................  Administrative Law Judge
Company.....................  Tennessee Gas Pipeline Company and its subsidiaries
Court of Appeals............  United States Court of Appeals for the District of Columbia
                              Circuit
EBIT........................  Earnings before interest expense and income taxes, excluding
                              affiliated interest income
EPA.........................  United States Environmental Protection Agency
EPEC........................  El Paso Energy Corporation, the indirect parent of Tennessee
                              Gas Pipeline Company
EPTPC.......................  El Paso Tennessee Pipeline Co., a direct subsidiary of El
                              Paso Energy Corporation and parent of Tennessee Gas Pipeline
                              Company
FERC........................  Federal Energy Regulatory Commission
GSR.........................  Gas supply realignment
PCB(s)......................  Polychlorinated biphenyl(s)
PRP(s)......................  Potentially responsible party(ies)
TGP.........................  Tennessee Gas Pipeline Company, a wholly owned subsidiary of
                              El Paso Tennessee Pipeline Co.
</TABLE>

                                        i
<PAGE>   3

                        PART I -- FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

                         TENNESSEE GAS PIPELINE COMPANY

                  CONDENSED CONSOLIDATED STATEMENTS OF INCOME
                                 (IN MILLIONS)
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                                                 QUARTER           NINE MONTHS
                                                                  ENDED               ENDED
                                                              SEPTEMBER 30,       SEPTEMBER 30,
                                                              --------------      --------------
                                                              1999     1998       1999     1998
                                                              -----    -----      -----    -----
<S>                                                           <C>      <C>        <C>      <C>
Operating revenues..........................................  $164     $165       $526     $522
                                                              ----     ----       ----     ----
Operating expenses
  Operation and maintenance.................................    53       62        127      196
  Depreciation, depletion, and amortization.................    34       34        102      101
  Taxes, other than income taxes............................     9       10         33       31
                                                              ----     ----       ----     ----
                                                                96      106        262      328
                                                              ----     ----       ----     ----
Operating income............................................    68       59        264      194
                                                              ----     ----       ----     ----
Other income, net...........................................    (3)     (11)       (15)     (22)
                                                              ----     ----       ----     ----
Income before interest, income taxes and discontinued
  operations................................................    71       70        279      216
                                                              ----     ----       ----     ----
Non-affiliated interest and debt expense....................    26       26         90       76
Affiliated interest (income) expense, net...................    (3)      13        (19)      48
Income tax expense..........................................    15        7         67       27
                                                              ----     ----       ----     ----
                                                                38       46        138      151
                                                              ----     ----       ----     ----
Income before discontinued operations.......................    33       24        141       65
Discontinued operations, net of income taxes................    --       22         --       58
                                                              ----     ----       ----     ----
Net income..................................................  $ 33     $ 46       $141     $123
                                                              ====     ====       ====     ====
</TABLE>

              The accompanying Notes are an integral part of these
                  Condensed Consolidated Financial Statements.

                                        1
<PAGE>   4

                         TENNESSEE GAS PIPELINE COMPANY

                     CONDENSED CONSOLIDATED BALANCE SHEETS
                      (IN MILLIONS, EXCEPT SHARE AMOUNTS)

<TABLE>
<CAPTION>
                                                              SEPTEMBER 30,   DECEMBER 31,
                                                                  1999            1998
                                                              -------------   ------------
                                                               (UNAUDITED)
<S>                                                           <C>             <C>
                                          ASSETS
Current assets
  Cash and cash equivalents.................................     $    3          $    5
  Accounts and notes receivable, net........................        159             137
  Materials and supplies....................................         17              15
  Deferred income tax benefit...............................         46              38
  Other.....................................................         14              33
                                                                 ------          ------
          Total current assets..............................        239             228
Property, plant, and equipment, net.........................      4,439           4,440
Other.......................................................        195             188
                                                                 ------          ------
          Total assets......................................     $4,873          $4,856
                                                                 ======          ======

LIABILITIES AND STOCKHOLDER'S EQUITY

Current liabilities
  Accounts payable..........................................     $  295          $  242
  Short-term borrowings (including current maturities of
     long-term debt)........................................         21             191
  Deferred credits..........................................         54             136
  Other.....................................................        165             121
                                                                 ------          ------
          Total current liabilities.........................        535             690
                                                                 ------          ------
Long-term debt, less current maturities.....................      1,353           1,353
                                                                 ------          ------
Deferred income taxes.......................................      1,178           1,150
                                                                 ------          ------
Other.......................................................        281             278
                                                                 ------          ------

Commitments and contingencies (See Note 3)

Stockholder's equity
  Common stock, par value $5 per share; authorized 300
     shares; issued 208 shares..............................         --              --
  Additional paid-in capital................................      1,385           1,385
  Retained earnings.........................................        141              --
                                                                 ------          ------
          Total stockholder's equity........................      1,526           1,385
                                                                 ------          ------
          Total liabilities and stockholder's equity........     $4,873          $4,856
                                                                 ======          ======
</TABLE>

              The accompanying Notes are an integral part of these
                  Condensed Consolidated Financial Statements.

                                        2
<PAGE>   5

                         TENNESSEE GAS PIPELINE COMPANY

                CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                                 (IN MILLIONS)
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                                                NINE MONTHS
                                                                   ENDED
                                                               SEPTEMBER 30,
                                                              ----------------
                                                              1999       1998
                                                              -----      -----
<S>                                                           <C>        <C>
Cash flows from operating activities
  Net income................................................  $ 141      $ 123
  Less income from discontinued operations, net of income
     taxes..................................................     --         58
                                                              -----      -----
Income from continuing operations...........................    141         65
  Adjustments to reconcile net income to net cash from
     operating activities
     Depreciation, depletion, and amortization..............    102        101
     Deferred income taxes..................................     20         38
     Other..................................................      1        (11)
  Working capital changes...................................     24        192
  Other.....................................................      1        (45)
                                                              -----      -----
     Cash provided by continuing operations.................    289        340
     Cash used in discontinued operations...................     --        (79)
                                                              -----      -----
          Net cash provided by operating activities.........    289        261
                                                              -----      -----
Cash flows from investing activities
  Capital expenditures......................................    (90)       (59)
  Investment in joint ventures and equity investees.........    (12)       (10)
  Net change in advances to EPEC............................    (10)      (346)
  Other.....................................................     (8)         5
  Cash provided by investing activities of discontinued
     operations.............................................     --        250
                                                              -----      -----
          Net cash used in investing activities.............   (120)      (160)
                                                              -----      -----
Cash flows from financing activities
  Net commercial paper repayments...........................   (170)        --
  Net proceeds from affiliated note.........................     --        185
  Revolving credit repayments...............................     --       (117)
  Long-term debt retirements................................     (1)        --
  Cash used in financing activities by discontinued
     operations.............................................     --       (192)
                                                              -----      -----
          Net cash used in financing activities.............   (171)      (124)
                                                              -----      -----
Decrease in cash and temporary investments..................     (2)       (23)
  Less decrease in cash and temporary investments related to
     discontinued operations................................     --        (21)
                                                              -----      -----
  Decrease in cash and temporary investments from continuing
     operations.............................................     (2)        (2)
Cash and temporary investments
  Beginning of period.......................................      5         11
                                                              -----      -----
  End of period.............................................  $   3      $   9
                                                              =====      =====
</TABLE>

              The accompanying Notes are an integral part of these
                  Condensed Consolidated Financial Statements.

                                        3
<PAGE>   6

                         TENNESSEE GAS PIPELINE COMPANY

              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                  (UNAUDITED)

1. BASIS OF PRESENTATION

     The 1998 Annual Report on Form 10-K for the Company includes a summary of
significant accounting policies and other disclosures and should be read in
conjunction with this Quarterly Report on Form 10-Q. The condensed consolidated
financial statements at September 30, 1999, and for the quarters and nine months
ended September 30, 1999 and 1998 are unaudited. The condensed consolidated
balance sheet at December 31, 1998, is derived from audited financial statements
at that date. These financial statements do not include all disclosures required
by generally accepted accounting principles, but have been prepared pursuant to
the rules and regulations of the U.S. Securities and Exchange Commission. In the
opinion of management, all material adjustments necessary to present fairly the
results of operations for such periods have been included. All such adjustments,
except for those relating to discontinued operations described below, are of a
normal, recurring nature. Results of operations for any interim period are not
necessarily indicative of the results of operations for the entire year due to
the seasonal nature of the Company's businesses. Financial statements for the
previous periods include certain reclassifications which were made to conform to
the current presentation. Such reclassifications have no effect on reported net
income or stockholder's equity.

  Tax-free Internal Reorganization (Discontinued Operations)

     On December 31, 1998, EPEC completed a series of steps to effect a tax-free
internal reorganization. The Company has treated the assets and operations
distributed to EPEC or other subsidiaries of EPEC in the tax-free internal
reorganization as though they were discontinued operations as of December 31,
1998. Accordingly, the information for the quarter and nine months ended
September 30, 1998, in these financial statements has been presented as though
the transactions occurred on January 1, 1998. Revenues related to those items
treated as discontinued operations were $1,296 million and $3,518 million for
the quarter and nine months ended September 30, 1998, respectively.

2. DEBT AND OTHER CREDIT FACILITIES

     In August 1999, EPEC established a new $1,250 million 364-day renewable
revolving credit and competitive advance facility. As of September 30, 1999,
EPEC's interest rate on this facility was equal to LIBOR plus 50 basis points.
The rate will vary based on EPEC's long-term unsecured debt rating. This
facility replaced EPEC's $750 million 364-day renewable revolving credit and
competitive advance facility established in October 1997. TGP is a designated
borrower under this credit facility. As of September 30, 1999, no amounts were
outstanding under this facility.

     The weighted average interest rate of short-term borrowings was 5.5% and
5.8% at September 30, 1999 and December 31, 1998, respectively. The Company had
short-term borrowings, including current maturities of long-term debt, at
September 30, 1999 and December 31, 1998, as follows:

<TABLE>
<CAPTION>
                                                              1999    1998
                                                              -----   -----
                                                              (IN MILLIONS)
<S>                                                           <C>     <C>
Commercial paper............................................   $20    $190
Current maturities of long-term debt........................     1       1
                                                               ---    ----
                                                               $21    $191
                                                               ===    ====
</TABLE>

3. COMMITMENTS AND CONTINGENCIES

  Rates and Regulatory Matters

     In July 1998, FERC issued a Notice of Proposed Rulemaking ("NOPR") in which
it sought comments on a wide range of initiatives to change the manner in which
short-term (less than one year) transportation
                                        4
<PAGE>   7

markets are regulated. Among other things, the NOPR proposes the following: (i)
removing the price cap for the short-term capacity market; (ii) establishing
procedures to make pipeline and shipper-owned capacity comparable; (iii)
auctioning all available short-term pipeline capacity on a daily basis with the
pipeline unable to set a reserve price above variable costs; (iv) changing
policies or pipeline penalties, nomination procedures and services; (v)
increasing pipeline reporting requirements; (vi) permitting the negotiation of
terms and conditions of service; and (vii) potentially modifying the procedures
for certificating new pipeline construction. Also in July 1998, FERC issued a
Notice of Inquiry ("NOI") seeking comments on FERC's policy for pricing
long-term capacity. The Company provided comments on the NOPR and NOI in April
1999.

     In April 1997, FERC approved the settlement of all issues related to the
recovery of TGP's GSR and other transition costs and related proceedings (the
"GSR Stipulation and Agreement"). Under the terms of the GSR Stipulation and
Agreement, TGP is entitled to collect up to $770 million from its customers,
$693 million through a demand surcharge and $77 million through an interruptible
transportation surcharge. The demand portion has been fully collected. As of
September 30, 1999, $45 million of the interruptible transportation portion had
been collected. There is no time limit for collection of the interruptible
transportation surcharge. The terms of the GSR Stipulation and Agreement also
provide for a rate case moratorium through November 2000 (subject to certain
limited exceptions) and an escalating rate cap, indexed to inflation, through
October 2005, for certain of TGP's customers. In March 1999, TGP filed a GSR
reconciliation report with FERC in accordance with the terms of its GSR
Stipulation and Agreement. The report indicated that collections from firm
customers through the demand surcharge were $14 million more than the $693
million TGP was entitled to collect. In June 1999, FERC accepted the report as
complying with the GSR Stipulation and Agreement, and in July 1999, TGP refunded
the overcollections to its firm customers. TGP will be required to refund to
firm customers amounts collected in excess of each firm customer's share of the
final transition costs based on the final GSR reconciliation report, which will
be filed in March 2001. Any future refund is not expected to have a material
adverse effect on the Company's financial position, results of operations, or
cash flows.

     In December 1994, TGP filed for a general rate increase with FERC and in
October 1996, FERC approved a settlement resolving that proceeding. The
settlement included a structural rate design change that results in a larger
portion of TGP's transportation revenues being dependent upon throughput. One
party, a competitor of TGP, filed a Petition for Review of the FERC approved
settlement with the Court of Appeals, which subsequently remanded the case to
FERC to respond to the competitor's argument that TGP's cost allocation
methodology deterred the development of market centers (centralized locations
where buyers and sellers can physically exchange gas). At FERC's request,
comments were filed in January 1999. This matter is still pending before FERC.

     All cost of service issues related to TGP's 1991 general rate proceeding
were resolved pursuant to a settlement agreement approved by FERC which now has
become final. In a subsequent ruling, FERC remanded to an ALJ the issue of the
proper allocation of TGP's New England lateral costs. In October 1998, FERC
issued an order establishing the proper allocation of the New England lateral
costs and in April 1999 FERC denied requests for rehearing of that order. The
methodology approved by FERC economically approximates the methodology
previously used by TGP. In April 1999, TGP filed with FERC revised rates to be
effective May 1, 1999 consistent with the FERC's decision. TGP refunded
approximately $1 million to certain of its customers in the third quarter of
1999. The refunds resolved this proceeding.

     In April 1999, FERC approved a settlement which resolved all outstanding
FERC proceedings relating to the cashout reports that TGP had filed for the
period September 1993 through August 1998. The settlement also established a new
cashout mechanism to account for customer imbalances. The new cashout mechanism
was implemented in the second quarter of 1999, retroactive to September 1998.

     As previously reported, contracts representing 70 percent of TGP's firm
transportation capacity were due to expire by November 2000. As a result of
negotiations with existing customers to extend or restructure these contracts,
those contracts expiring by November 2000 now only represent approximately 20
percent of firm transportation capacity. To date, the conditions of settlements
and extensions have been similar to the original

                                        5
<PAGE>   8

contracts. Currently, 80 percent of TGP's contracted firm transportation
capacity has an average term in excess of four years. TGP continues to pursue
future markets and customers for the capacity that is not committed beyond
November 2000 and expects that this capacity will be placed under a combination
of long term and short term contracts. However, there can be no assurance as to
whether TGP will be able to replace these contracts or that the terms of new
contracts will be as favorable to TGP as the existing contracts.

     As an interstate pipeline, TGP is subject to FERC audits of its books and
records. As part of an industry-wide initiative, TGP's property retirements are
currently under review by the FERC audit staff.

     As the aforementioned rate and regulatory matters are fully and
unconditionally resolved, the Company may either recognize an additional refund
obligation or a non-cash benefit to finalize previously estimated liabilities.
Management believes the ultimate resolutions of these matters, which are in
various stages of finalization, will not have a material adverse effect on the
Company's financial position, results of operations, or cash flows.

  Legal Proceedings

     In February 1998, the United States and the State of Texas filed in a
United States District Court a Comprehensive Environmental Response,
Compensation and Liability Act ("CERCLA" or "Superfund") cost recovery action
against fourteen companies including the Company and certain of its affiliated
companies relating to the Sikes Disposal Pits Superfund Site ("Sikes") located
in Harris County, Texas. The suit claims that the United States and the State of
Texas have expended over $125 million in remediating the site, and seeks to
recover that amount plus interest from all defendants to the suit. Although
factual investigation relating to Sikes is in the preliminary stages, the
Company believes that the amount of material, if any, disposed at Sikes by the
Company was small, possibly de minimis. However, the plaintiffs have alleged
that the defendants are each jointly and severally liable for the entire
remediation costs and have also sought a declaration of liability for future
response costs such as groundwater monitoring. While the outcome of this matter
cannot be predicted with certainty, management does not expect this matter to
have a material adverse effect on the Company's financial position, results of
operations, or cash flows.

     TGP is a party in proceedings involving federal and state authorities
regarding the past use by TGP of a lubricant containing PCBs in its starting air
systems. TGP has executed a consent order with the EPA governing the remediation
of certain of its compressor stations and is working with the EPA and the
relevant states regarding those remediation activities. TGP is also working with
the Pennsylvania and New York environmental agencies regarding remediation and
post-remediation activities at the Pennsylvania and New York stations.
Management believes that the ultimate resolution of these matters will not have
a material adverse effect on the Company's financial position, results of
operations, or cash flows.

     In November 1988, the Kentucky environmental agency filed a complaint in a
Kentucky state court alleging that TGP discharged pollutants into the waters of
the state without a permit and disposed of PCBs without a permit. The agency
sought an injunction against future discharges, sought an order to remediate or
remove PCBs, and sought a civil penalty. TGP has entered into agreed orders with
the agency to resolve many of the issues raised in the original allegations, has
received water discharge permits for its Kentucky compressor stations from the
agency, and continues to work to resolve the remaining issues. The relevant
Kentucky compressor stations are scheduled to be characterized and remediated
under the consent order with the EPA. Management believes that the resolution of
this issue will not have a material adverse effect on the Company's financial
position, results of operations, or cash flows.

     A number of subsidiaries of EPEC, both wholly and partially owned,
including the Company, have been named defendants in actions brought by Jack
Grynberg on behalf of the U.S. Government under the False Claims Act. Generally,
the complaints allege an industry-wide conspiracy to underreport the heating
value as well as the volumes of the natural gas produced from federal and Indian
lands, thereby depriving the U.S. Government of royalties. The Company believes
the complaint to be without merit and that the ultimate resolution of this issue
will not have a material adverse effect on the Company's financial position,
results of operations, or cash flows.

                                        6
<PAGE>   9

     The Company is a named defendant in numerous lawsuits and a named party in
numerous governmental proceedings arising in the ordinary course of business.
While the outcome of such lawsuits or other proceedings cannot be predicted with
certainty, management currently does not expect these matters to have a material
adverse effect on the Company's financial position, results of operations, or
cash flows.

  Environmental

     The Company is subject to extensive federal, state, and local laws and
regulations governing environmental quality and pollution control. These laws
and regulations require the Company to remove or remedy the effect on the
environment of the disposal or release of specified substances at current and
former operating sites. As of September 30, 1999, the Company had reserves of
approximately $111 million for expected environmental costs.

     In addition, the Company estimates that its subsidiaries will make capital
expenditures for environmental matters of approximately $4 million for the
remainder of 1999. These expenditures primarily relate to compliance with air
regulations and, to a lesser extent, control of water discharges. The Company
expects to incur expenditures of approximately $95 million in the aggregate for
the years 2000 through 2007.

     Since 1988, TGP has been engaged in an internal project to identify and
deal with the presence of PCBs and other substances of concern, including
substances on the EPA List of Hazardous Substances, at compressor stations and
other facilities operated by both its interstate and intrastate natural gas
pipeline systems. While conducting this project, TGP has been in frequent
contact with federal and state regulatory agencies, both through informal
negotiation and formal entry of consent orders, to assure that its efforts meet
regulatory requirements.

     In May 1995, following negotiations with its customers, TGP filed with FERC
a Stipulation and Agreement (the "Environmental Stipulation") that establishes a
mechanism for recovering a substantial portion of the environmental costs
identified in the internal project. The Environmental Stipulation was effective
July 1, 1995. As of September 30, 1999, all amounts have been collected under
the Environmental Stipulation. Refunds may be required to the extent actual
eligible expenditures are less than estimated eligible expenditures used to
determine amounts collected under the Environmental Stipulation.

     The Company and certain of its subsidiaries have been designated, have
received notice that they could be designated, or have been asked for
information to determine whether they could be designated as a PRP with respect
to 3 sites under CERCLA or state equivalents. The Company has sought to resolve
its liability as a PRP with respect to these Superfund sites through
indemnification by third parties and/or settlements which provide for payment of
the Company's allocable share of remediation costs. Since the clean-up costs are
estimates and are subject to revision as more information becomes available
about the extent of remediation required, and because in some cases the Company
has asserted a defense to any liability, the Company's estimate of its share of
remediation costs could change. Moreover, liability under the federal Superfund
statute is joint and several, meaning that the Company could be required to pay
in excess of its pro rata share of remediation costs. The Company's
understanding of the financial strength of other PRPs has been considered, where
appropriate, in the determination of its estimated liability. The Company
presently believes that the costs associated with the current status of such
other entities as PRPs at the Superfund sites referenced above will not have a
material adverse effect on the Company's financial position, results of
operations, or cash flows.

     The Company has initiated proceedings against its historic liability
insurers seeking payment or reimbursement of costs and liabilities associated
with various environmental matters. In these proceedings, the Company contends
that certain environmental costs and liabilities associated with various
entities or sites, including costs associated with former operating sites, must
be paid or reimbursed by certain of its historic insurers. The proceedings are
in the discovery stage, and it is not yet possible to predict the outcome.

     It is possible that new information or future developments could require
the Company to reassess its potential exposure related to environmental matters.
The Company may incur significant costs and liabilities in order to comply with
existing environmental laws and regulations. It is also possible that other
developments, such as increasingly strict environmental laws, regulations and
enforcement policies thereunder,

                                        7
<PAGE>   10

and claims for damages to property, employees, other persons and the environment
resulting from current or discontinued operations, could result in substantial
costs and liabilities in the future. As such information becomes available, or
other relevant developments occur, related accrual amounts will be adjusted
accordingly. While there are still uncertainties relating to the ultimate costs
which may be incurred, based upon the Company's evaluation and experience to
date, the Company believes the recorded reserves are adequate.

     Other than the items discussed above, management is not aware of any other
commitments or contingent liabilities which would have a material adverse effect
on the Company's financial condition, results of operations, or cash flows.

4. PROPERTY, PLANT, AND EQUIPMENT

     Property, plant, and equipment at September 30, 1999 and December 31, 1998,
consisted of the following:

<TABLE>
<CAPTION>
                                                               1999     1998
                                                              ------   ------
                                                               (IN MILLIONS)
<S>                                                           <C>      <C>
Property, plant, and equipment, at cost.....................  $2,333   $2,316
Less accumulated depreciation and depletion.................     200      216
                                                              ------   ------
                                                               2,133    2,100
Additional acquisition cost assigned to utility plant, net
  of accumulated amortization...............................   2,306    2,340
                                                              ------   ------
          Total property, plant, and equipment, net.........  $4,439   $4,440
                                                              ======   ======
</TABLE>

     Current FERC policy does not permit the Company to recover amounts in
excess of original cost allocated in purchase accounting to its regulated
operations through rates.

5. NEW ACCOUNTING PRONOUNCEMENTS NOT YET ADOPTED

  Accounting for Derivative Instruments and Hedging Activities

     In June 1998, Statement of Financial Accounting Standards No. 133,
Accounting for Derivative Instruments and Hedging Activities, was issued by the
Financial Accounting Standards Board to establish accounting and reporting
standards for derivative instruments, including certain derivative instruments
embedded in other contracts, and for hedging activities. This pronouncement
requires that an entity classify all derivatives as either assets or liabilities
in the statement of financial position and measure those instruments at fair
value. If certain conditions are met, a derivative may be specifically
designated as (i) a hedge of the exposure to changes in the fair value of a
recognized asset or liability or an unrecognized firm commitment, (ii) a hedge
of the exposure to variable cash flows of a forecasted transaction, or (iii) a
hedge of the foreign currency exposure of a net investment in a foreign
operation, an unrecognized firm commitment, an
available-for-sale security or a foreign-currency-denominated forecasted
transaction. The accounting for the changes in the fair value of a derivative
depends on the intended use of the derivative and the resulting designation. The
standard was amended by Statement of Financial Accounting Standards No. 137
issued in June 1999. The amendment defers the effective date to fiscal years
beginning after June 15, 2000. The Company is currently evaluating the effects
of this pronouncement.

                                        8
<PAGE>   11

ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
        OF OPERATIONS

     The information contained in Item 2 updates, and should be read in
conjunction with, information set forth in Part II, Items 7, 7A, and 8, in the
Company's Annual Report on Form 10-K for the year ended December 31, 1998, in
addition to the interim condensed consolidated financial statements and
accompanying notes presented in Item 1 of this Quarterly Report on Form 10-Q.

                                    GENERAL

     On December 31, 1998, EPEC completed a tax-free internal reorganization of
its assets and operations and those of its subsidiaries. Following the
reorganization, the Company's primary asset was the interstate pipeline system
known as the TGP System. See Note 1 for a further discussion of the tax-free
internal reorganization.

                        RESULTS OF CONTINUING OPERATIONS

<TABLE>
<CAPTION>
                                                        QUARTER        NINE MONTHS
                                                         ENDED            ENDED
                                                     SEPTEMBER 30,    SEPTEMBER 30,
                                                     -------------    --------------
                                                     1999    1998     1999     1998
                                                     ----    -----    -----    -----
                                                              (IN MILLIONS)
<S>                                                  <C>     <C>      <C>      <C>
Operating revenues.................................  $164    $ 165    $ 526    $ 522
Operating expenses.................................   (96)    (106)    (262)    (328)
Other, net.........................................     3       11       15       22
                                                     ----    -----    -----    -----
  EBIT.............................................  $ 71    $  70    $ 279    $ 216
                                                     ====    =====    =====    =====
</TABLE>

  THIRD QUARTER 1999 COMPARED TO THIRD QUARTER 1998

     Operating expenses for the quarter ended September 30, 1999, were $10
million lower than for the same period of 1998. This decrease was attributable
to lower system fuel usage associated with operating efficiencies achieved as a
result of lower throughput levels and lower direct operating and maintenance
costs.

     Other, net for the quarter ended September 30, 1999, was $8 million lower
than for the same period of 1998 primarily due to interest income on a favorable
sales and use tax settlement received in the third quarter of 1998 and lower
earnings from equity investments in the third quarter of 1999.

  NINE MONTHS ENDED 1999 COMPARED TO NINE MONTHS ENDED 1998

     Operating revenues for the nine months ended September 30, 1999, were $4
million higher than for the same period of 1998 primarily due to the favorable
resolution of regulatory issues during 1999 and the impact of a downward
revision in the amount of recoverable interest on GSR costs in 1998. The
increase was partially offset by a favorable customer settlement in the second
quarter of 1998 and lower system throughput in 1999 due to milder temperatures.

     Operating expenses for the nine months ended September 30, 1999, were $66
million lower than for the same period of 1998. The decrease was primarily due
to the favorable resolution of certain regulatory issues during 1999 and lower
fuel usage associated with operating efficiencies achieved as a result of lower
system throughput levels and lower direct operating and maintenance costs.

     Other, net for the nine months ended September 30, 1999, was $7 million
lower than for the same period of 1998 primarily due to interest income received
in the third quarter of 1998 on a favorable sales and use tax settlement and
lower earnings from equity investments during 1999. The decrease was partially
offset by the impact of a favorable settlement of a regulatory issue in the
first quarter of 1999.

                                        9
<PAGE>   12

NON-AFFILIATED INTEREST AND DEBT EXPENSE

     Non-affiliated interest and debt expense for nine months ended September
30, 1999, was higher than for the same period of 1998 primarily due to an
increase in long-term borrowings.

AFFILIATED INTEREST (INCOME) EXPENSE, NET

     Affiliated interest income, net for the quarter and nine months ended
September 30, 1999, was higher than for the same period of 1998 due to the
reduction of affiliated debt and increased advances to EPEC.

INCOME TAX EXPENSE

  Third Quarter 1999 Compared to Third Quarter 1998

     The effective tax rate for the quarter ended September 1999, was higher
than the rate for the same period of 1998 in part because of a favorable
settlement, regarding a state income tax refund claim, received in 1998.
Additionally, the effective tax rate for the quarter ended September 1998 was
lower than the same period in 1999 as a result of equity income from
unconsolidated foreign affiliates for which no provision for U.S. income tax is
required.

                                     OTHER

  YEAR 2000

     EPEC has established an executive steering committee and a project team to
coordinate the phases of its Year 2000 project to assure that the Company's key
automated systems, equipment, and related processes will remain functional
through the Year 2000. Those phases are: (i) awareness; (ii) assessment; (iii)
remediation; (iv) testing; (v) implementation of the necessary modifications and
(vi) contingency planning. The Company has participated in EPEC's Year 2000
project as described below.

     In recognition of the importance of Year 2000 issues and their potential
impact on the Company, the initial phase of the Year 2000 project involved the
establishment of a company-wide awareness program. The awareness program is
directed by the executive steering committee and project team and includes
participation of senior management in each core business area. The awareness
phase is substantially completed, although the Company will continually update
awareness efforts for the duration of the Year 2000 project.

     The Company's assessment phase consists of conducting a company-wide
inventory of its key automated systems and related processes, analyzing and
assigning levels of criticality to those systems and processes, identifying and
prioritizing resource requirements, developing validation strategies and testing
plans, and evaluating business partner relationships. The assessment phase is
substantially complete. The assessment phase of the project, among other things,
involves efforts to obtain representations and assurances from third parties,
including third party vendors, that their hardware and equipment products,
embedded chip systems, and software products being used by or impacting the
Company are or will be modified to be Year 2000 compliant. Increasingly, the
responses from such third parties are generally encouraging. Nonetheless, many
of these responses lack the substantive detail to allow the Company to make a
meaningful evaluation of such third-parties' Year 2000 readiness. Furthermore,
in some circumstances, third parties are refusing to provide any response beyond
those contained in their publicly-disseminated information. As a result, the
overall evaluation of the Company's business partners' Year 2000 readiness
remains inconclusive. Accordingly, the Company cannot predict the potential
consequences if these or other third parties or their products are not Year 2000
compliant. The Company continues to evaluate the exposure associated with such
business partner relationships, and will use the contingency planning process to
attempt to mitigate the uncertainty concerning third-party readiness.

     The remediation phase involves converting, modifying, replacing or
eliminating key automated systems identified in the assessment phase. The
testing phase involves the validation of the identified key automated systems.
The Company is utilizing test tools and written test procedures to document and
validate, as

                                       10
<PAGE>   13

necessary, its unit, system, integration and acceptance testing. The
implementation phase involves placing the converted or replaced key automated
systems into operation. One system that was not substantially complete with
respect to Year 2000 issues as of June 30, 1999, was the nominations, scheduling
and volume accounting applications utilized by TGP. That system is now
substantially complete. In October 1999, the Company, in cooperation with other
Interstate Natural Gas Association of America members, reported that its
regulated pipeline will be Year 2000 compliant on the rollover date of January
1, 2000. The Company is substantially complete with its remediation, testing and
implementation phases for its systems.

     The Company had previously identified the contingency planning phase as a
subset of the implementation phase, but has now established the process as its
own phase of the overall Year 2000 program. The contingency planning phase
consists of developing a risk profile of the Company's critical business
processes and then providing for actions the Company will pursue to keep such
processes operational in the event of Year 2000 disruptions. The focus of such
contingency planning is on prompt response to any Year 2000 events, and a plan
for subsequent resumption of normal operations. The plan attempts to assess the
risk of a significant failure to critical processes performed by the Company,
and to address the mitigation of those risks. The plan will also consider any
significant failures related to the most reasonably likely worst case scenario,
discussed below, as they may occur. In addition, the plan attempts to factor in
the severity and duration of the impact of a significant failure. The Company
has developed contingency plans for each business unit and significant business
process. By September 30, 1999, the Company had conducted desk-top testing of
its contingency plans and had conducted drills and mock outages, including some
testing with certain customers and other significant third parties. The Year
2000 contingency plans will continue to be tested, modified and adjusted
throughout the year as additional information becomes available.

     The goal of the Year 2000 project is to ensure that all of the critical
systems and processes which are under the Company's direct control remain
functional. Certain systems and processes may be interrelated with or dependent
upon systems outside the Company's control. However, systems within the
Company's control may also have unpredicted problems. Accordingly, there can be
no assurance that significant disruptions will be avoided. The Company's present
analysis of its most reasonably likely worst case scenario for Year 2000
disruptions includes sporadic Year 2000 failures in the telecommunications and
electricity industries, as well as interruptions from suppliers that might cause
disruptions in the Company's operations, thus causing temporary financial losses
and an inability to deliver products and services to customers. Virtually all of
the natural gas transported through the Company's interstate pipelines is owned
by third parties. Accordingly, failures of natural gas producers to be ready for
the Year 2000 could significantly disrupt the flow of product to the Company's
customers. In many cases, the producers have no direct contractual relationship
with the Company, and the Company relies on its customers to verify the Year
2000 readiness of the producers from whom they purchase natural gas. Since most
of the Company's revenues from the delivery of natural gas are based upon fees
paid by its customers for the reservation of capacity, and not based upon the
volume of actual deliveries, short-term disruptions in deliveries caused by
factors beyond the Company's control should not have a significant financial
impact on the Company, although it could cause operational problems for the
Company's customers. Longer-term disruptions, however, could materially impact
the Company's results of operations, financial condition, and cash flows.

     While the total cost of the Company's Year 2000 project continues to be
evaluated, the Company estimates that the costs remaining to be incurred in 1999
and 2000 associated with assessing, remediating and testing internally developed
computer applications, hardware and equipment, embedded chip systems, and
third-party-developed software will be between $1 million and $2 million. Of
these estimated costs, the Company expects to capitalize up to $1 million. As of
September 30, 1999, the Company has incurred expenses of approximately $4
million and has capitalized costs of approximately $3 million. The Company has
previously only traced incremental expenses related to its Year 2000 project.
This means that the costs of the Year 2000 project related to salaried employees
of the Company, including their direct salaries and benefits, are not available,
and have not been included in the estimated costs of the project. Since the
earlier phases of the project mostly involved work performed by such salaried
employees, the costs expended to date do not reflect the percentage completion
of the project. The Company anticipates that it will expend a substantial amount
of the remaining costs in the contingency planning phase of the project,
including the potential

                                       11
<PAGE>   14

acquisition of back-up assets and systems that may be deployed in the event
primary systems fail to perform fully according to expectations.

     Although the Company does not expect the costs of its Year 2000 project,
including any costs remaining to be expended for the readiness of assets
formerly owned by Sonat, to have a material adverse effect on its financial
position, results of operations, or cash flows, based on information available
at this time the Company cannot conclude that disruption caused by internal or
external Year 2000 related failures will not have such an effect. Specific
factors which might affect the success of the Company's Year 2000 efforts and
the frequency or severity of a Year 2000 disruption or the amount of expense
include the failure of the Company or its outside consultants to properly
identify deficient systems, the failure of the selected remedial action to
adequately address the deficiencies, the failure of the Company or its outside
consultants to complete the remediation in a timely manner (due to shortages of
qualified labor or other factors), the failure of other parties to joint
ventures in which the Company is involved to meet their obligations, both
financial and operational, under the relevant joint venture agreements to
remediate assets used by the joint venture, unforeseen expenses related to the
remediation of existing systems or the transition to replacement systems, the
failure of third parties to become Year 2000 compliant or to adequately notify
the Company of potential noncompliance and the effects of any significant
disruption at international facilities in which the Company has significant
investments.

     The above disclosure is a "YEAR 2000 READINESS DISCLOSURE" made with the
intention to comply fully with the Year 2000 Information and Readiness
Disclosure Act of 1998, Pub. L. No. 105-271, 112 Stat, 2386, signed into law
October 19, 1998. All statements made herein shall be construed within the
confines of that Act. To the extent that any reader of the above Year 2000
Readiness Disclosure is other than an investor or potential investor in the
Company's -- or an affiliate's -- equity or debt securities, this disclosure is
made for the SOLE PURPOSE of communicating or disclosing information aimed at
correcting, helping to correct and/or avoiding Year 2000 failures.

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

     This report contains forward-looking statements within the meaning of the
Private Securities Litigation Reform Act of 1995. Where any such forward-looking
statement includes a statement of the assumptions or bases underlying such
forward-looking statement, the Company cautions that, while such assumptions or
bases are believed to be reasonable and are made in good faith, assumed facts or
bases almost always vary from the actual results, and the differences between
assumed facts or bases and actual results can be material, depending upon the
circumstances. Where, in any forward-looking statement, the Company or its
management expresses an expectation or belief as to future results, such
expectation or belief is expressed in good faith and is believed to have a
reasonable basis, but there can be no assurance that the statement of
expectation or belief will result or be achieved or accomplished. The words
"believe," "expect," "estimate," "anticipate" and similar expressions may
identify forward-looking statements.

     Important factors that could cause actual results to differ materially from
those in the forward-looking statements herein include increasing competition
within the Company's industry, the timing and extent of changes in commodity
prices for natural gas and power, uncertainties associated with customer
contract expirations on the TGP pipeline system, uncertainties associated with
acquisitions and joint ventures, potential environmental liabilities, potential
contingent liabilities and tax liabilities related to the Company's
acquisitions, political and economic risks associated with current and future
operations in foreign countries, conditions of the equity and other capital
markets during the periods covered by the forward-looking statements, and other
risks, uncertainties and factors, including the effect of the Year 2000 date
change, discussed more completely in the Company's other filings with the U.S.
Securities and Exchange Commission, including its Annual Report on Form 10-K for
the year ended December 31, 1998.

                                       12
<PAGE>   15

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

     The information contained in Item 3 updates, and should be read in
conjunction with, information set forth in Part II, Item 7A in the Company's
Annual Report on Form 10-K for the year ended December 31, 1998, in addition to
the interim consolidated financial statements, accompanying notes, and
Management's Discussion and Analysis of Financial Condition and Results of
Operations presented in Items 1 and 2 of this Quarterly Report on Form 10-Q.

     There have been no material changes in market risk faced by the Company
from those reported in the Company's Annual Report on Form 10-K for the year
ended December 31, 1998.

                                       13
<PAGE>   16

                          PART II -- OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS

     See Part I, Financial Information, Note 3, which is incorporated herein by
reference.

ITEM 2. CHANGES IN SECURITIES AND USE OF PROCEEDS.

     None.

ITEM 3. DEFAULTS UPON SENIOR SECURITIES

     None.

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

     None.

ITEM 5. OTHER INFORMATION

     None.

ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K

a. Exhibits

     Each exhibit identified below is filed as a part of this report.

<TABLE>
<CAPTION>
        EXHIBIT
         NUMBER                                  DESCRIPTION
        -------                                  -----------
<C>                      <S>
          10.A           -- $1,250,000,000 364-Day Revolving Credit and Competitive
                            Advance Facility Agreement dated as of August 16, 1999,
                            by and among EPEC, EPNG, TGP, the several banks and other
                            financial institutions from time to time parties to the
                            Agreement, The Chase Manhattan Bank, as administrative
                            agent and as CAF Advance Agent for the Lenders
                            thereunder, Citibank N.A. and ABN Amro Bank, N.V. as
                            co-documentation agents for the Lenders and Bank of
                            America, N.A. as syndication agent for the Lenders.
          27             -- Financial Data Schedule
</TABLE>

     Undertaking

          The undersigned hereby undertakes, pursuant to Regulation S-K, Item
     601(b), paragraph (4)(iii), to furnish to the U.S. Securities and Exchange
     Commission, upon request, all constituent instruments defining the rights
     of holders of long-term debt of TGP and its consolidated subsidiaries not
     filed herewith for the reason that the total amount of securities
     authorized under any of such instruments does not exceed 10 percent of the
     total consolidated assets of TGP and its consolidated subsidiaries.

b. Reports on Form 8-K

     None.

                                       14
<PAGE>   17

                                   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.

                                            TENNESSEE GAS PIPELINE COMPANY

Date: November 12, 1999                            /s/ H. BRENT AUSTIN
                                            ------------------------------------
                                                      H. Brent Austin
                                                Executive Vice President and
                                                  Chief Financial Officer

Date: November 12, 1999                           /s/ JEFFREY I. BEASON
                                            ------------------------------------
                                                     Jeffrey I. Beason
                                            Senior Vice President and Controller
                                                 (Chief Accounting Officer)

                                       15
<PAGE>   18

                               INDEX TO EXHIBITS

<TABLE>
<CAPTION>
        EXHIBIT
         NUMBER                                  DESCRIPTION
        -------                                  -----------
<C>                      <S>
          10.A           -- $1,250,000,000 364-Day Revolving Credit and Competitive
                            Advance Facility Agreement dated as of August 16, 1999,
                            by and among EPEC, EPNG, TGP, the several banks and other
                            financial institutions from time to time parties to the
                            Agreement, The Chase Manhattan Bank, as administrative
                            agent and as CAF Advance Agent for the Lenders
                            thereunder, Citibank N.A. and ABN Amro Bank, N.V. as
                            co-documentation agents for the Lenders and Bank of
                            America, N.A. as syndication agent for the Lenders.
          27             -- Financial Data Schedule
</TABLE>