<PAGE>

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                                 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 MARCH 31, 2002

                                       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 1-2745

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

                          SOUTHERN NATURAL GAS COMPANY
             (Exact Name of Registrant as Specified in its Charter)

<Table>
<S>                                                 <C>
                     DELAWARE                                           63-0196650
          (State or Other Jurisdiction of                            (I.R.S. Employer
          Incorporation or Organization)                            Identification No.)
</Table>

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

                        Telephone Number: (713) 420-2600

     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 $3.75 per share. Shares outstanding on May 10,
2002: 1,000

     SOUTHERN NATURAL GAS 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.

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<PAGE>

                        PART I -- FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

                          SOUTHERN NATURAL GAS COMPANY

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

<Table>
<Caption>
                                                              QUARTER ENDED
                                                                MARCH 31,
                                                              --------------
                                                              2002      2001
                                                              ----      ----
<S>                                                           <C>       <C>
Operating revenues..........................................  $103      $111
                                                              ----      ----
Operating expenses
  Operation and maintenance.................................    37        46
  Depreciation, depletion and amortization..................    11        10
  Taxes, other than income taxes............................     5         6
                                                              ----      ----
                                                                53        62
                                                              ----      ----
Operating income............................................    50        49
                                                              ----      ----
Other income
  Earnings from unconsolidated affiliates...................     3         3
  Other, net................................................     2         3
                                                              ----      ----
                                                                 5         6
                                                              ----      ----
Income before interest and income taxes.....................    55        55
                                                              ----      ----
Non-affiliated interest and debt expense....................    13        11
Affiliated interest income..................................    (1)       (4)
Income tax expense..........................................    16        18
                                                              ----      ----
                                                                28        25
                                                              ----      ----
Net income..................................................  $ 27      $ 30
                                                              ====      ====
</Table>

                            See accompanying notes.

                                        1
<PAGE>

                          SOUTHERN NATURAL GAS COMPANY

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

<Table>
<Caption>
                                                               MARCH 31,    DECEMBER 31,
                                                                 2002           2001
                                                              -----------   ------------
<S>                                                           <C>           <C>
                                         ASSETS

Current assets
  Cash and cash equivalents.................................    $   --         $   --
  Accounts and notes receivable, net
     Customer...............................................        50             58
     Affiliates.............................................       593            372
     Other..................................................         7             13
  Materials and supplies....................................        14             13
  Regulatory assets.........................................        31             31
  Other.....................................................         2             --
                                                                ------         ------
          Total current assets..............................       697            487
                                                                ------         ------
Property, plant and equipment, at cost......................     2,664          2,642
  Less accumulated depreciation, depletion and
     amortization...........................................     1,303          1,304
                                                                ------         ------
          Total property, plant and equipment, net..........     1,361          1,338
                                                                ------         ------
Other assets
  Investments in unconsolidated affiliates..................       119            116
  Other.....................................................        19             23
                                                                ------         ------
                                                                   138            139
                                                                ------         ------
          Total assets......................................    $2,196         $1,964
                                                                ======         ======

                          LIABILITIES AND STOCKHOLDER'S EQUITY

Current liabilities
  Accounts payable
     Trade..................................................    $   32         $   37
     Affiliates.............................................         8              7
     Other..................................................         2              3
  Current maturities of long-term debt......................       100            200
  Taxes payable.............................................        59             48
  Accrued interest..........................................        20             28
  Other.....................................................         6              1
                                                                ------         ------
          Total current liabilities.........................       227            324
                                                                ------         ------
Long-term debt, less current maturities.....................       798            499
                                                                ------         ------
Other liabilities
  Deferred income taxes.....................................       173            169
  Other.....................................................        44             45
                                                                ------         ------
                                                                   217            214
                                                                ------         ------
Commitments and contingencies
Stockholder's equity
  Common stock, par value $3.75 per share; authorized and
     issued 1,000 shares....................................        --             --
  Additional paid-in capital................................       105            105
  Retained earnings.........................................       849            822
                                                                ------         ------
          Total stockholder's equity........................       954            927
                                                                ------         ------
          Total liabilities and stockholder's equity........    $2,196         $1,964
                                                                ======         ======
</Table>

                            See accompanying notes.

                                        2
<PAGE>

                          SOUTHERN NATURAL GAS COMPANY

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

<Table>
<Caption>
                                                               QUARTER ENDED
                                                                 MARCH 31,
                                                              ----------------
                                                              2002       2001
                                                              -----      -----
<S>                                                           <C>        <C>
Cash flows from operating activities
  Net income................................................  $  27      $  30
  Adjustments to reconcile net income to net cash from
     operating activities
     Depreciation, depletion and amortization...............     11         10
     Deferred income tax expense............................      4          4
     Undistributed earnings of unconsolidated affiliates....     (3)        (3)
  Working capital changes...................................     22         10
  Non-working capital changes and other.....................     --        (13)
                                                              -----      -----
          Net cash provided by operating activities.........     61         38
                                                              -----      -----
Cash flows from investing activities
  Additions to property, plant and equipment................    (37)       (17)
  Net change in affiliated advances receivable..............   (222)      (225)
  Net proceeds from the sale of assets......................      1          7
                                                              -----      -----
          Net cash used in investing activities.............   (258)      (235)
                                                              -----      -----
Cash flows from financing activities
  Payments to retire long-term debt.........................   (100)      (100)
  Net proceeds from the issuance of long-term debt..........    297        297
                                                              -----      -----
          Net cash provided by financing activities.........    197        197
                                                              -----      -----
Net change in cash and cash equivalents.....................     --         --
Cash and cash equivalents
  Beginning of period.......................................     --         --
                                                              -----      -----
  End of period.............................................  $  --      $  --
                                                              =====      =====
</Table>

                            See accompanying notes.

                                        3
<PAGE>

                          SOUTHERN NATURAL GAS COMPANY

              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                  (UNAUDITED)

1. BASIS OF PRESENTATION

     Our 2001 Annual Report on Form 10-K includes a summary of our significant
accounting policies and other disclosures. You should read it in conjunction
with this Quarterly Report on Form 10-Q. The financial statements as of March
31, 2002, and for the quarters ended March 31, 2002 and 2001, are unaudited. The
balance sheet as of December 31, 2001, is derived from the audited balance sheet
filed in our Form 10-K. These financial statements have been prepared pursuant
to the rules and regulations of the U.S. Securities and Exchange Commission and
do not include all disclosures required by accounting principles generally
accepted in the United States. In our opinion, we have made all adjustments, all
of which are of a normal, recurring nature, to fairly present our interim period
results. Information for interim periods may not necessarily indicate the
results of operations for the entire year due to the seasonal nature of our
businesses. The prior period information also includes reclassifications which
were made to conform to the current period presentation. These reclassifications
have no effect on our reported net income or stockholders' equity.

     Our accounting policies are consistent with those discussed in our Form
10-K.

2. DEBT AND OTHER CREDIT FACILITIES

     We had the following current maturities of long-term debt:

<Table>
<Caption>
                                                              MARCH 31,   DECEMBER 31,
                                                                2002          2001
                                                              ---------   ------------
                                                                   (IN MILLIONS)
<S>                                                           <C>         <C>
Current maturities of long-term debt........................    $100          $200
                                                                ====          ====
</Table>

     In January 2002, we filed a shelf registration statement increasing the
amount of debt we can issue from $100 million to $300 million. In February 2002,
we issued $300 million aggregate principal amount of 8.0% notes due 2032. Net
proceeds were approximately $297 million, net of issuance costs. This issuance
used the remaining capacity on our shelf registration statement, and proceeds
were used to pay off $100 million of our 7.85% notes due 2002 and for other
general purposes.

     In May 2002, we repaid $100 million of our 8.625% notes due 2002.

3. COMMITMENTS AND CONTINGENCIES

  Legal Proceedings

     In 1997, we and a number of our affiliates were named defendants in actions
brought by Jack Grynberg on behalf of the U.S. Government under the False Claims
Act. Generally, these complaints allege an industry-wide conspiracy to under
report the heating value as well as the volumes of the natural gas produced from
federal and Native American lands, which deprived the U.S. Government of
royalties. These matters have been consolidated for pretrial purposes (In re:
Natural Gas Royalties Qui Tam Litigation, U.S. District Court for the District
of Wyoming, filed June 1997). In May 2001, the court denied the defendants'
motions to dismiss.

     We and a number of our affiliates were named defendants in Quinque
Operating Company, et al v. Gas Pipelines and Their Predecessors, et al, filed
in 1999 in the District Court of Stevens County, Kansas. This class action
complaint alleges that the defendants mismeasured natural gas volumes and
heating content of natural gas on non-federal and non-Native American lands. The
Quinque complaint was transferred to the same court handling the Grynberg
complaint and has now been sent back to Kansas State Court for further
proceedings. A motion to dismiss this case is pending.

     We are also a named defendant in numerous lawsuits and a named party in
numerous governmental proceedings arising in the ordinary course of our
business.

                                        4
<PAGE>

     While the outcome of the matters discussed above cannot be predicted with
certainty, based on information known to date, we do not expect the ultimate
resolution of these matters will have a material adverse effect on our ongoing
financial position, operating results or cash flows.

  Environmental Matters

     We are subject to extensive federal, state and local laws and regulations
governing environmental quality and pollution control. These laws and
regulations require us 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 March 31, 2002, we had a reserve of approximately $9 million for
expected remediation costs. In addition, we expect to make capital expenditures
for environmental matters of approximately $7 million in the aggregate for the
years 2002 through 2007. These expenditures primarily relate to compliance with
clean air regulations.

     We have been designated and have received notice that we could be
designated, or have been asked for information to determine whether we could be
designated, as a Potentially Responsible Party with respect to one active site
under the Comprehensive Environmental Response, Compensation and Liability Act
or state equivalents. We are currently evaluating our potential share, if any,
of the remediation costs.

     It is possible that new information or future developments could require us
to reassess our potential exposure related to environmental matters. We 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 and regulations and claims for
damages to property, employees, other persons and the environment resulting from
our current or past operations, could result in substantial costs and
liabilities in the future. As this information becomes available, or other
relevant developments occur, we will adjust our accrual amounts accordingly.
While there are still uncertainties relating to the ultimate costs we may incur,
based on our evaluation and experience to date, we believe the recorded reserves
are adequate.

  Rates and Regulatory Matters

     In February 2000, the Federal Energy Regulatory Commission (FERC) issued
Order No. 637 which revised regulations regarding capacity release, capacity
segmentation, imbalance management services, operational flow orders and
pipeline penalties. On July 2, 2001, we filed a settlement addressing our
compliance with Order No. 637. We received an order on the settlement from the
FERC on April 11, 2002. The FERC approved our settlement, subject to
modifications related to our segmentation proposal, and rejected our proposed
changes to our cash-out mechanism. We are seeking rehearing and will make
another compliance filing subject to the outcome of our rehearing request.

     In March 2000, the FERC issued an order which authorized the
recommissioning of our Elba Island Liquefied Natural Gas (LNG) receiving
terminal near Savannah, Georgia. In July 2001, the FERC issued a final order
approving a modification of the sendout facilities at the terminal subject to
several conditions. In October 2001, we received an initial cargo of LNG in
order to test the facilities. In October 2001, we also applied to increase Elba
Island's initial rates to reflect an increase in capital and expenses, primarily
associated with expenditures mandated by the FERC. In November 2001, the FERC
authorized us to commence service on December 1, 2001, but denied our October
2001 request to amend the initial rates, indicating that the increase should be
filed in a limited Section 4 proceeding. In December 2001, we filed a limited
proceeding with the FERC to increase rates and received an order accepting the
new rates effective March 1, 2002, subject to refund. The increase in capital
over the previously approved level is approximately $43 million. A major
intervener is currently opposing this increase in cost, and this proceeding is
set for a hearing in November 2002. We have established estimated monthly
reserve levels that represent revenues collected subject to refund.

     In May 2000, we filed an application with the FERC to expand our pipeline
system by 336 million cubic feet of natural gas per day at an estimated cost of
$141 million to serve new power generation loads being sited adjacent to our
system. We received a certificate order from the FERC in March 2001. In July
2001, the FERC approved an amendment to the project, which reduced its cost
slightly. The Alabama Municipal

                                        5
<PAGE>

Distributors Group and others filed appeals of the FERC's orders authorizing
this project in the D.C. Circuit Court of Appeals.

     In September 2001, the FERC issued a Notice of Proposed Rulemaking (NOPR).
The NOPR proposes to apply the standards of conduct governing the relationship
between interstate pipelines and marketing affiliates to all energy affiliates.
The proposed regulations, if adopted by the FERC, would dictate how all our
energy affiliates conduct business and interact with our interstate pipelines.
In December 2001, we filed comments with the FERC addressing our concerns with
the proposed rules. In April 2002, the FERC Staff issued a notice of a public
conference to be held on May 21, 2002, at which interested parties will be given
an opportunity to comment further on the NOPR. We cannot predict the outcome of
the NOPR, but adoption of the regulations in substantially the form proposed
would, at a minimum, place additional administrative and operational burdens on
us.

     In October 2001, we filed an application with the FERC to expand our south
system by 359.8 million cubic feet of natural gas per day at an estimated cost
of $247 million, to serve existing, new and expanded gas-fired electric
generation facilities. The construction will be undertaken in two phases, with a
target in-service date for the Phase I facilities of June 1, 2003, and for the
Phase II facilities of May 1, 2004. Two shippers subsequently requested a delay
in the commencement of their services, and one shipper requested a reduced
service quantity. As a result, in April 2002, we filed an amendment to the
certificate application to reflect these changes. This application remains
pending before the FERC.

4. RELATED PARTY TRANSACTIONS

     We participate in El Paso Corporation's cash management program which
matches short-term cash surpluses and needs of its participating affiliates,
thus minimizing total borrowing from outside sources. We had advanced $593
million at March 31, 2002, at a market rate of interest which was 1.9%. At
December 31, 2001, we had advanced $371 million at a market rate of interest
which was 2.1%.

     At December 31, 2001, we had accounts receivable from affiliates of $1
million. In addition, we had accounts payable to affiliates of $8 million at
March 31, 2002, and $7 million at December 31, 2001. These balances arose in the
normal course of business.

5. NEW ACCOUNTING PRONOUNCEMENTS ISSUED BUT NOT YET ADOPTED

  Accounting for Asset Retirement Obligations

     In August 2001, the Financial Accounting Standards Board issued Statement
of Financial Accounting Standards No. 143, Accounting for Asset Retirement
Obligations. This Statement requires companies to record a liability relating to
the retirement and removal costs of assets used in their business. The liability
is discounted to its present value, and the related asset value is increased by
the amount of the resulting liability. Over the life of the asset, the liability
will be accreted to its future value and eventually extinguished when the asset
is taken out of service. Capitalized retirement and removal costs will be
depreciated over the useful life of the related asset. The provisions of this
Statement are effective for fiscal years beginning after June 15, 2002. We are
currently evaluating the effects of this pronouncement.

                                        6
<PAGE>

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

     The information contained in Item 2 updates, and you should read it in
conjunction with, information disclosed in our Annual Report on Form 10-K filed
March 20, 2002, in addition to the financial statements and notes presented in
Item 1, Financial Statements, of this Quarterly Report on Form 10-Q.

                             RESULTS OF OPERATIONS

     Below are the operating results and an analysis of these results for the
quarters ended March 31:

<Table>
<Caption>
                                                               2002         2001
                                                              -------      -------
                                                              (IN MILLIONS, EXCEPT
                                                                VOLUME AMOUNTS)
<S>                                                           <C>          <C>
Operating revenues..........................................  $  103       $  111
Operating expenses..........................................     (53)         (62)
Other income, net...........................................       5            6
                                                              ------       ------
  Earnings before interest expense and income taxes.........  $   55       $   55
                                                              ======       ======
Throughput volumes (BBtu/d)(1)..............................   2,283        2,231
                                                              ======       ======
</Table>

---------------
(1) BBtu/d means billion British thermal units per day.

     In March 2000, the FERC issued an order allowing us to reactivate our Elba
Island LNG facility. The facility received its first LNG shipment in October
2001 and was officially placed in service on December 1, 2001.

     Operating revenues for the quarter ended March 31, 2002, were $8 million
lower than the same period in 2001. The decrease is primarily due to lower
prices in the first quarter of 2002 on sales under natural gas purchase
contracts and on sales of excess natural gas recoveries. Partially offsetting
the decrease were revenues from our Elba Island facility which was placed in
service in December 2001 and increased throughput from our interruptible
transportation service in 2002.

     Operating expenses for the quarter ended March 31, 2002, were $9 million
lower than the same period in 2001 primarily due to lower purchased natural gas
costs due to lower prices in the first quarter of 2002. The decrease was
partially offset by higher operating expenses from our Elba Island facility and
higher corporate overhead allocations in the first quarter of 2002.

INTEREST AND DEBT EXPENSE

  Non-Affiliated Interest and Debt Expense

     Non-affiliated interest and debt expense for the quarter ended March 31,
2002, was $2 million higher than the same period in 2001 due to increased net
long-term borrowings in the first quarter of 2002.

  Affiliated Interest Income

     Affiliated interest income, net for the quarter ended March 31, 2002, was
$3 million lower than the same period in 2001 primarily due to lower short-term
interest rates in 2002 on average advances to El Paso Corporation under our cash
management program.

INCOME TAXES

     The income tax expense for the quarters ended March 31, 2002 and 2001, was
$16 million and $18 million, resulting in effective tax rates of 37 percent and
38 percent. Our effective tax rates were different than the statutory rate of 35
percent primarily due to state income taxes.

                                        7
<PAGE>

                         COMMITMENTS AND CONTINGENCIES

     See Item 1, Financial Statements, Note 3, which is incorporated herein by
reference.

                 NEW ACCOUNTING PRONOUNCEMENTS NOT YET ADOPTED

     See Item 1, Financial Statements, Note 5, which is incorporated herein by
reference.

                                        8
<PAGE>

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

     This report contains or incorporates by reference forward-looking
statements within the meaning of the Private Securities Litigation Reform Act of
1995. Where any forward-looking statement includes a statement of the
assumptions or bases underlying the forward-looking statement, we caution that,
while we believe these assumptions or bases to be reasonable and to be 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, we or our management express an expectation or belief as to future
results, that expectation or belief is expressed in good faith and is believed
to have a reasonable basis. We cannot assure you, however, that the statement of
expectation or belief will result or be achieved or accomplished. The words
"believe," "expect," "estimate," "anticipate" and similar expressions will
generally identify forward-looking statements.

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

     This information updates, and you should read it in conjunction with,
information disclosed in Part II, Item 7A in our Annual Report on Form 10-K for
the year ended December 31, 2001, in addition to the information presented in
Items 1 and 2 of this Quarterly Report on Form 10-Q.

     There are no material changes in our quantitative and qualitative
disclosures about market risks from those reported in our Annual Report on Form
10-K for the year ended December 31, 2001.

                                        9
<PAGE>

                          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

     None.

     Undertaking

          We hereby undertake, 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 our long-term debt not filed herewith for the reason that the
     total amount of securities authorized under any of such instruments does
     not exceed 10 percent of our total consolidated assets.

b. Reports on Form 8-K

     We filed a current report on Form 8-K dated February 26, 2002, filing
exhibits in connection with an offering of $300 million in 8.0% notes due March
1, 2032.

                                        10
<PAGE>

                                   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.

                                            SOUTHERN NATURAL GAS COMPANY

Date: May 10, 2002                             /s/ JOHN W. SOMERHALDER II
                                            ------------------------------------
                                                   John W. Somerhalder II
                                             Chairman of the Board and Director

Date: May 10, 2002                                 /s/ GREG G. GRUBER
                                            ------------------------------------
                                                       Greg G. Gruber
                                                   Senior Vice President,
                                                Chief Financial Officer and
                                                         Treasurer
                                            (Principal Financial and Accounting
                                                          Officer)

                                        11