<PAGE>

                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                    FORM 10-Q

QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT
OF 1934

For the quarterly period ended MARCH 31, 2000


                        Commission File Number: 000-26091
                                TC PIPELINES, LP
             (Exact name of registrant as specified in its charter)



                Delaware                                  52-2135448
-------------------------------                 ----------------------------
(State or other jurisdiction of incorporation   (I.R.S. Employer
or organization)                                Identification Number)


203, 110 Turnpike Road
Westborough, Massachusetts                                 01581
-------------------------------                  ----------------------------
(Address of principal executive offices)                 (Zip code)


                                 508-871-7046
                  --------------------------------------------
               Registrant's telephone number, including area code


     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 report(s), and (2) has been subject to such
filing requirements for the past 90 days. Yes [X] No [ ]


     As of May 10, 2000 there were 14,690,694 of the registrant's common units
outstanding.


<PAGE>

                                TC PIPELINES, LP

                                TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                                                             Page No.
                                                                                             --------
<S>           <C>                                                                     <C>
PART I.  FINANCIAL INFORMATION

     ITEM 1.  Financial Statements


              Statement of Income - Three months ended March 31, 2000                            3
              Balance Sheet - March 31, 2000 and December 31, 1999                               3
              Statement of Cash Flows - Three months ended March 31, 2000                        4
              Notes to Condensed Financial Statements                                            5

     ITEM 2.  Management's Discussion and Analysis of Financial Condition and
              Results of Operations

              Results of Operations of TC PipeLines, LP                                          7
              Liquidity and Capital Resources of TC PipeLines, LP                                7
              Results of Operations of Northern Border Pipeline Company                          9
              Liquidity and Capital Resources of Northern Border Pipeline Company               10

     ITEM 3.  Quantitative and Qualitative Disclosures about Market Risk                        12

PART II.  OTHER INFORMATION

     ITEM 6.  Exhibits and Reports on Form 8-K                                                  13



</TABLE>

                                       2

<PAGE>

                          PART I. FINANCIAL INFORMATION

                          ITEM 1. FINANCIAL STATEMENTS

                                TC PIPELINES, LP

                               STATEMENT OF INCOME
<TABLE>
<CAPTION>

(UNAUDITED)                                                                                THREE MONTHS ENDED
(THOUSANDS OF DOLLARS, EXCEPT PER UNIT AMOUNT)                                                 MARCH 31, 2000
------------------------------------------------------------------------------------ ------------------------
<S>                                                                                  <C>
EQUITY INCOME FROM INVESTMENT IN NORTHERN BORDER PIPELINE COMPANY                                       8,623
GENERAL AND ADMINISTRATIVE EXPENSES                                                                       279
                                                                                     ------------------------
NET INCOME                                                                                              8,344
                                                                                     ------------------------
                                                                                     ------------------------
NET INCOME ALLOCATION
Common units                                                                                            6,864
Subordinated units                                                                                      1,313
General partner                                                                                           167
                                                                                     ------------------------
                                                                                                        8,344
                                                                                     ------------------------
                                                                                     ------------------------
NET INCOME PER UNIT                                                                                     $0.47
                                                                                     ------------------------
                                                                                     ------------------------
UNITS OUTSTANDING (THOUSANDS)                                                                          17,500
                                                                                     ------------------------
                                                                                     ------------------------
</TABLE>

                                  BALANCE SHEET

<TABLE>
<CAPTION>
                                                                               MARCH 31, 2000    December 31,
(THOUSANDS OF DOLLARS)                                                            (unaudited)            1999
------------------------------------------------------------------------- -------------------  --------------
<S>                                                                       <C>                  <C>

ASSETS
Cash                                                                                    1,654             795
Investment in Northern Border Pipeline Company                                        249,812         250,450
                                                                          -------------------  --------------
                                                                                      251,466         251,245
                                                                          -------------------  --------------
                                                                          -------------------  --------------
-------------------------------------------------------------------------------------------------------------

LIABILITIES AND PARTNERS' CAPITAL
Current Liabilities
   Accounts payable                                                                       320             407
                                                                          -------------------  --------------
                                                                                          320             407
                                                                          -------------------  --------------
Partners' Capital
   Common units                                                                       208,827         208,573
   Subordinated units                                                                  37,296          37,248
   General partner                                                                      5,023           5,017
                                                                          -------------------  --------------
                                                                                      251,146         250,838
                                                                          -------------------  --------------
                                                                                      251,466         251,245
                                                                          -------------------  --------------
                                                                          -------------------  --------------
</TABLE>

             See accompanying Notes to Condensed Financial Statements.

                                       3

<PAGE>


                    PART I. FINANCIAL INFORMATION (CONTINUED)

                     ITEM 1. FINANCIAL STATEMENTS (CONTINUED)

                                TC PIPELINES, LP

                             STATEMENT OF CASH FLOWS

<TABLE>
<CAPTION>

(UNAUDITED)                                                                                THREE MONTHS ENDED
(THOUSANDS OF DOLLARS)                                                                         MARCH 31, 2000
------------------------------------------------------------------------------------ ------------------------
<S>                                                                                  <C>

CASH GENERATED FROM OPERATIONS
Net income                                                                                              8,344
Add/(Deduct):
Distributions received in excess of equity income                                                         638
Increase in operating working capital                                                                     (87)
                                                                                     ------------------------
                                                                                                        8,895
                                                                                     ------------------------

FINANCING ACTIVITIES
Distributions paid                                                                                     (8,036)
                                                                                     ------------------------
                                                                                                       (8,036)
                                                                                     ------------------------

INCREASE IN CASH                                                                                          859

CASH, BEGINNING OF PERIOD                                                                                 795
                                                                                     ------------------------

CASH, END OF PERIOD                                                                                     1,654
                                                                                     ------------------------
                                                                                     ------------------------

</TABLE>

            See accompanying Notes to Condensed Financial Statements.

                                       4

<PAGE>
                    PART I. FINANCIAL INFORMATION (CONTINUED)

                    ITEM 1. FINANCIAL STATEMENTS (CONTINUED)

                                TC PIPELINES, LP

                     NOTES TO CONDENSED FINANCIAL STATEMENTS
                    FOR THE THREE MONTHS ENDED MARCH 31, 2000
                                   (unaudited)

NOTE 1     BASIS OF PRESENTATION
TC PipeLines, LP, a Delaware limited partnership, and its subsidiary limited
partnership, TC PipeLines Intermediate Limited Partnership, a Delaware limited
partnership, are collectively referred to herein as TC PipeLines or the
Partnership.

       The financial statements have been prepared by management in accordance
with United States generally accepted accounting principles. Amounts are stated
in United States dollars.

       Since a determination of many assets, liabilities, revenues and expenses
is dependent upon future events, the preparation of these financial statements
requires the use of estimates and assumptions which have been made using careful
judgment. In the opinion of management, these financial statements have been
properly prepared within reasonable limits of materiality and include all
adjustments (consisting primarily of normal recurring accruals) necessary to
present fairly the financial position of the Partnership as at March 31, 2000
and December 31, 1999 and the results of operations and cash flows for the three
months ended March 31, 2000.

       The results of operations for the three months ended March 31, 2000 are
not necessarily indicative of the results that may be expected for a full fiscal
year.

NOTE 2 FORMATION OF PARTNERSHIP
The Partnership commenced operations on May 28, 1999 when it issued 14,300,000
common units (11,500,000 to the public and 2,800,000 to an affiliate of the
general partner) for net proceeds of $274.6 million, after deducting
underwriters' fees of $15.0 million. These proceeds, along with 3,200,000
subordinated units, a 2% general partner interest and incentive distribution
rights, were issued to TransCanada Border PipeLine Ltd. and TransCan Northern
Ltd. (collectively, the predecessor companies), affiliates of the general
partner, to acquire the predecessor companies' 30% general partner interest in
Northern Border Pipeline Company.

         On June 25, 1999, the underwriters exercised a portion of their
over-allotment option under the terms of the underwriting agreement and
purchased 390,694 additional common units for net proceeds of $7.5 million. The
Partnership used those proceeds to redeem 390,694 subordinated units from the
general partner.

         The common units and the subordinated units represent limited
partner interests in the Partnership. During the period which subordinated
units are outstanding (the subordination period), to the extent there is
sufficient available cash, the holders of common units are entitled to
receive a minimum quarterly distribution (MQD), plus any arrearages on the
common units, before any distribution is made to the holders of subordinated
units. The holders of subordinated units will have the right to receive the
MQD only after the common units have received the MQD plus any arrearages in
payment of the MQD. The subordinated units are not entitled to arrearages.
Upon expiration of the subordination period, which will generally not occur
before June 30, 2004, the subordinated units will convert into common units
on a one-for-one basis and will then participate pro rata with the other
common units in distributions of available cash.

         The holder of the general partner interest is entitled to receive 2% of
total cash distributions until the MQD has been achieved, at which time it will
have the right to receive incentive distributions. Incentive distribution rights
represent the right to receive an increasing percentage of quarterly
distributions of available cash after the MQD has been achieved.

NOTE 3 INVESTMENT IN NORTHERN BORDER PIPELINE COMPANY
The Partnership owns a 30% general partner interest in Northern Border Pipeline
Company (Northern Border Pipeline), a partnership which owns a natural gas
pipeline extending from the Montana-Saskatchewan border near Port of Morgan,
Montana, to a terminus near Manhattan, Illinois. Northern Border Pipeline is
subject to regulation by the Federal Energy Regulatory Commission. Northern
Border Pipeline's accounting policies conform to United States generally
accepted accounting principles, as applied in the case of regulated entities.

                                     5


<PAGE>



                    PART I. FINANCIAL INFORMATION (CONTINUED)

                    ITEM 1. FINANCIAL STATEMENTS (CONCLUDED)

                                TC PIPELINES, LP

         The Partnership uses the equity method of accounting for its investment
in Northern Border Pipeline, over which it is able to exercise significant
influence. TC PipeLines' equity income for the three months ended March 31, 2000
represents 30% of the net income of Northern Border Pipeline for the same
period.

         The following sets out summarized financial information for Northern
Border Pipeline for the three months ended March 31, 2000 and as at March 31,
2000 and December 31, 1999. TC PipeLines has held its general partner interest
since May 28, 1999.

<TABLE>
<CAPTION>
(UNAUDITED)                                                                           Three months ended
(MILLIONS OF DOLLARS)                                                                     March 31, 2000
------------------------------------------------------------------------------- -------------------------
<S>                                                                                    <C>
NORTHERN BORDER PIPELINE INCOME STATEMENT
Revenues                                                                                           76.2
Costs and expenses                                                                                (16.8)
Depreciation                                                                                      (14.8)
Financial charges and other                                                                       (15.9)
                                                                                -------------------------
Net income                                                                                         28.7
                                                                                -------------------------
</TABLE>

<TABLE>
<CAPTION>
                                                                       MARCH 31, 2000       December 31,
(MILLIONS OF DOLLARS)                                                     (unaudited)               1999
------------------------------------------------------------------ -------------------- -----------------
<S>                                                                     <C>                 <C>
NORTHERN BORDER PIPELINE BALANCE SHEET
Cash and cash equivalents                                                        39.4              17.3
Other current assets                                                             38.4              33.8
Plant, property and equipment, net                                            1,713.6           1,731.4
Other assets                                                                     14.0              14.2
Current liabilities                                                           (113.1)            (116.7)
Reserves and deferred credits                                                  (10.5)             (10.7)
Long-term debt                                                                (849.1)            (834.5)
                                                                   -------------------- -----------------
Partners' capital                                                               832.7             834.8
                                                                   -------------------- -----------------
</TABLE>

NOTE 4 CREDIT FACILITY
On May 28, 1999, the Partnership entered into a $40 million unsecured two-year
revolving credit facility with TransCanada PipeLine USA Ltd., an affiliate of
the general partner. At March 31, 2000, the Partnership had no amount
outstanding under this credit facility.

NOTE 5 NET INCOME PER UNIT
Net income per unit is computed by dividing net income, after deduction of the
general partner's allocation, by the number of common and subordinated units
outstanding.

                                      6

<PAGE>

                    PART I. FINANCIAL INFORMATION (CONTINUED)

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

                                TC PIPELINES, LP

RESULTS OF OPERATIONS OF TC PIPELINES, LP
TC PipeLines, LP (the Partnership) was formed by TransCanada PipeLines Limited
(TransCanada) to acquire, own and participate in the management of United States
based pipeline assets. On May 28, 1999, the Partnership issued 14,300,000 common
units (11,500,000 to the public and 2,800,000 to an affiliate of the general
partner) through its initial public offering for net proceeds of $274.6 million.
The Partnership used the net proceeds from this offering, along with 3,200,000
subordinated units, an aggregate 2% general partner interest and incentive
distribution rights, to acquire the collective 30% general partner interest in
Northern Border Pipeline Company (Northern Border Pipeline) previously held by
TransCanada Border PipeLine Ltd. and TransCan Northern Ltd. (collectively, the
predecessor companies), affiliates of the general partner, TC PipeLines GP, Inc.
The remaining 70% general partner interest in Northern Border Pipeline is held
by Northern Border Partners, L.P., a publicly traded limited partnership that is
not affiliated with TC PipeLines.

Subsequent to the initial public offering, the underwriters exercised a portion
of their over-allotment option and purchased 390,694 additional common units for
net proceeds of $7.5 million. The Partnership used these proceeds to redeem an
equal number of subordinated units held by the general partner.

Currently, the only material asset of the Partnership is the 30% general partner
interest in Northern Border Pipeline.

TC PipeLines, LP accounts for its interest in Northern Border Pipeline using the
equity method of accounting. The Partnership's initial investment in Northern
Border Pipeline was recorded at $241.7 million, the combined carrying values of
the investment in Northern Border Pipeline as reflected in the accounts of the
predecessor companies as at May 28, 1999. This amount equated to 30% of Northern
Border Pipeline's partners' capital as at May 28, 1999.

Since the general partner interest in Northern Border Pipeline is currently the
Partnership's only source of income, the Partnership's results of operations are
influenced by and reflect the same factors that influence the financial results
of Northern Border Pipeline.

FIRST QUARTER 2000
For the three months ended March 31, 2000, TC PipeLines recorded $8.6 million of
equity income from Northern Border Pipeline and incurred general and
administrative expenses of $0.3 million, resulting in net income of $8.3 million
for the first quarter of 2000.

LIQUIDITY AND CAPITAL RESOURCES OF TC PIPELINES, LP

CASH DISTRIBUTION POLICY OF TC PIPELINES, LP
During the subordination period, which generally cannot end before June 30,
2004, the Partnership will make distributions of available cash as defined in
the partnership agreement in the following manner:

      -  First, 98% to the common units, pro rata, and 2% to the general
         partner, until there has been distributed for each outstanding common
         unit an amount equal to the minimum quarterly distribution for that
         quarter;

      -  Second, 98% to the common units, pro rata, and 2% to the general
         partner, until there has been distributed for each outstanding common
         unit an amount equal to any arrearages in payment of the minimum
         quarterly distribution on the common units for that quarter and for any
         prior quarters during the subordination period;

                                     7
<PAGE>

                    PART I. FINANCIAL INFORMATION (CONTINUED)

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

                                TC PIPELINES, LP

      -  Third, 98% to the subordinated units, pro rata, and 2% to the
         general partner, until there has been distributed for each
         outstanding subordinated unit an amount equal to the minimum
         quarterly distribution for that quarter; and

      -  Thereafter, in a manner whereby the general partner has rights
         (referred to as incentive distribution rights) to receive increasing
         percentages of excess quarterly distributions over specified
         distribution thresholds.

FIRST QUARTER 2000
On February 14, 2000, TC PipeLines paid a cash distribution of $0.45 per unit
for the three months ended December 31, 1999 to unitholders of record as of
January 31, 2000. This cash distribution, totaling $8.0 million, was paid out
in the following manner: $6.6 million to common unitholders, $1.2 million to
the general partner as holder of the subordinated units, and $0.2 million to
the general partner in respect of its 2% general partner interest.

The Partnership funded this cash distribution with its share of Northern
Border Pipeline's fourth quarter 1999 cash distribution.

On April 17, 2000, the board of directors of the general partner declared a
cash distribution of $0.45 per unit for the three months ended March 31,
2000, which is payable on May 15, 2000 to unitholders of record as of April
28, 2000. This will amount to a cash distribution totaling $8.0 million,
which will be paid out in the following manner: $6.6 million to common
unitholders, $1.2 million to the general partner as holder of the
subordinated units, and $0.2 million to the general partner in respect of its
2% general partner interest.

The Partnership will fund this cash distribution with its share of Northern
Border Pipeline's first quarter 2000 cash distribution.

CREDIT FACILITY
On May 28, 1999, the Partnership entered into a $40 million unsecured
two-year revolving credit facility with TransCanada PipeLine USA Ltd., an
affiliate of the general partner. The credit facility bears interest at a
London Interbank Offered Rate plus 1.25%. The purpose of the revolving credit
facility is to provide borrowings to fund capital expenditures, to fund
capital contributions to Northern Border Pipeline and for working capital and
other general business purposes, including funding cash distributions to
partners, if necessary. At March 31, 2000, the Partnership had no amount
outstanding under this credit facility.

CAPITAL REQUIREMENTS
To the extent TC PipeLines has any capital requirements with respect to its
investment in Northern Border Pipeline or makes acquisitions in 2000, TC
PipeLines expects to finance these requirements with debt and/or equity.

NORTHERN BORDER PIPELINE CASH DISTRIBUTION POLICY
In accordance with Northern Border Pipeline's cash distribution policy, a
distribution for the fourth quarter ending December 31, 1999 was paid on
February 2, 2000. TC PipeLines, LP received $9.3 million, representing 30% of
that cash distribution.

In accordance with Northern Border Pipeline's cash distribution policy, a
distribution for the first quarter ending March 31, 2000 was paid on May 2,
2000. TC PipeLines, LP received $10.0 million, representing 30% of that cash
distribution.

                                       8

<PAGE>

                    PART I. FINANCIAL INFORMATION (CONTINUED)

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

                                TC PIPELINES, LP

RESULTS OF OPERATIONS OF NORTHERN BORDER PIPELINE COMPANY
The following sets out summarized financial information for Northern Border
Pipeline for the three months ended March 31, 2000 and as at March 31, 2000
and December 31, 1999. TC PipeLines, LP has held its 30% general partner
interest since May 28, 1999.

<TABLE>
<CAPTION>
(UNAUDITED)                                                                           THREE MONTHS ENDED
(MILLIONS OF DOLLARS)                                                                     MARCH 31, 2000
--------------------------------------------------------------------------------------------------------

<S>                                                                             <C>
NORTHERN BORDER PIPELINE INCOME STATEMENT
Revenues                                                                                           76.2
Costs and expenses                                                                                (16.8)
Depreciation                                                                                      (14.8)
Financial charges and other                                                                       (15.9)
                                                                                -------------------------
Net income                                                                                         28.7
                                                                                -------------------------
</TABLE>

<TABLE>
<CAPTION>
                                                                       MARCH 31, 2000       December 31,
(MILLIONS OF DOLLARS)                                                     (unaudited)               1999
---------------------------------------------------------------------------------------------------------

<S>                                                                <C>                  <C>
NORTHERN BORDER PIPELINE BALANCE SHEET
Cash and cash equivalents                                                        39.4              17.3
Other current assets                                                             38.4              33.8
Plant, property and equipment, net                                            1,713.6           1,731.4
Other assets                                                                     14.0              14.2
Current liabilities                                                            (113.1)           (116.7)
Reserves and deferred credits                                                   (10.5)            (10.7)
Long-term debt                                                                 (849.1)           (834.5)
                                                                   -------------------- -----------------
Partners' capital                                                               832.7             834.8
                                                                   -------------------- -----------------

</TABLE>

Northern Border Pipeline's revenue is derived from agreements with various
shippers for the transportation of natural gas. It transports gas under a
Federal Energy Regulatory Commission (FERC) regulated tariff that provides an
opportunity to recover all of the operations and maintenance costs of the
pipeline, taxes other than income taxes, interest, depreciation and
amortization, an allowance for income taxes and a regulated return on equity.
Northern Border Pipeline is generally allowed to collect from its shippers a
return on regulated rate base as well as recover that rate base through
depreciation and amortization. The return amount Northern Border Pipeline may
collect from its shippers declines as the rate base is recovered. Billings
for the firm transportation agreements are based on contracted volumes to
determine the allocable share of the cost of service and are not dependent
upon the percentage of available capacity actually used.

FIRST QUARTER 2000 COMPARED WITH FIRST QUARTER 1999
Revenues increased $2.6 million (4%) for the first quarter of 2000, as
compared to the same period in 1999, due primarily to recovery of increased
depreciation expense and interest expense.

Depreciation expense increased $2.1 million (16%) for the first quarter of
2000, as compared to the same period in 1999, due primarily to an increase in
the depreciation rate applied to transmission plant from 2.0% to 2.3%. The
increase in the depreciation rate was approved as part of a previous rate
case settlement.

Financial charges and other consists of interest expense, net and other
income.

                                       9

<PAGE>

                    PART I. FINANCIAL INFORMATION (CONTINUED)

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

                                TC PIPELINES, LP

Interest expense increased $1.9 million (13%) for the first quarter of 2000, as
compared to the same period in 1999, due primarily to an increase in interest
rates between 1999 and 2000.


LIQUIDITY AND CAPITAL RESOURCES OF NORTHERN BORDER PIPELINE COMPANY

GENERAL
In August 1999, Northern Border Pipeline completed a private offering of $200
million of 7.75% Senior Notes due 2009, which notes were subsequently
exchanged in a registered offering for notes with substantially identical
terms (Senior Notes). The proceeds from the Senior Notes were used to reduce
indebtedness under a June 1997 credit agreement.

In June 1997, Northern Border Pipeline entered into a credit agreement
(Pipeline Credit Agreement) with certain financial institutions. The Pipeline
Credit Agreement is comprised of a term loan and a $200 million five-year
revolving credit facility, both maturing in June 2002. At March 31, 2000,
$439.0 million was outstanding under the term loan and $15.0 million was
outstanding under the five-year revolving credit facility.

At March 31, 2000, Northern Border Pipeline also had outstanding $250 million
of senior notes issued in a private placement under a July 1992 note purchase
agreement. The note purchase agreement provides for four series of notes,
Series A through D, maturing between August 2000 and August 2003. The Series
A Notes with a principal amount of $66 million mature in August 2000.
Northern Border Pipeline anticipates borrowing on the revolving credit
facility to repay the Series A Notes.

Short-term liquidity needs will be met by internal sources and through the
revolving credit facility discussed above. Long-term capital needs may be met
through the ability to issue long-term indebtedness.

CASH FLOWS FROM OPERATING ACTIVITIES
Cash flows provided by operating activities increased $1.2 million to $38.4
million for the first quarter of 2000, as compared to the same period in
1999, primarily due to recovery of increased depreciation and amortization
expense and the billings collected subject to refund related to Northern
Border Pipeline's current rate proceeding. These increases were partially
offset by a reduction in working capital primarily due to a decrease in
accrued interest. Interest on the Senior Notes is payable semi-annually in
March and September.

CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures of $0.4 million for the first quarter of 2000 are
primarily related to Project 2000, an expansion and 34-mile extension of
Northern Border Pipeline's existing natural gas pipeline system. For the
comparable period in 1999, capital expenditures were $57.3 million and
included $51.9 for The Chicago Project, which was Northern Border Pipeline's
expansion and extension project placed in service in December 1998. The
remaining capital expenditures for 1999 were primarily related to renewals and
replacements of existing facilities.

Total capital expenditures for 2000 are estimated to be $27 million,
including $15 million for Project 2000. The remaining capital expenditures
planned for 2000 are for renewals and replacements of existing facilities.
Northern Border Pipeline currently anticipates funding its 2000 capital
expenditures primarily by using internal sources and borrowing on the
revolving credit facility.

                                      10


<PAGE>

                    PART I. FINANCIAL INFORMATION (CONTINUED)

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

                                TC PIPELINES, LP

CASH FLOWS FROM FINANCING ACTIVITIES
Cash flows used in financing activities were $16.0 million for the first quarter
of 2000 as compared to cash flows provided by financing activities of $27.0
million for the first quarter of 1999. Distributions paid to the general
partners decreased $7.1 million to $30.9 million for the first quarter of 2000
as compared to the same period of 1999. The distribution for 1999 included
distributions for four months activity, rather than three months, resulting from
a change in the timing of distribution payments. Borrowings under the Pipeline
Credit Agreement decreased $50 million for the first quarter of 2000 as compared
to the same period in 1999. Borrowings in 1999 were used to finance a portion of
the capital expenditures for The Chicago Project.

INFORMATION REGARDING FORWARD-LOOKING STATEMENTS
Certain statements in this Quarterly Report are forward-looking and relate
to, among other things, anticipated financial performance, business prospects
and strategies. Forward-looking information typically contains statements
with words such as "anticipate," "believe," "estimate," "expect," "plan,"
"target," or similar words suggesting future outcomes. By their nature, such
statements are subject to various risks and uncertainties that could cause TC
PipeLines, LP's actual results and experience to differ materially from the
anticipated results. Such risks and uncertainties include, but are not
limited to: regulatory decisions, particularly those of the Federal Energy
Regulatory Commission; future demand for natural gas; cost of acquisitions,
including related debt service payments; tariff and transportation charges to
be collected by Northern Border Pipeline for transportation services on the
Northern Border pipeline system; overcapacity in the industry; and prevailing
economic conditions, particularly conditions of the capital and equity
markets. For further information on additional risks and uncertainties, you
are advised to consult TC PipeLines, LP's 1999 Form 10-K under the heading
"Forward-Looking Information."

                                      11

<PAGE>

                    PART I. FINANCIAL INFORMATION (CONCLUDED)

       ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

                                TC PIPELINES, LP


For the three months ended March 31, 2000, TC PipeLines, LP has not entered into
any forms of financial instruments that are market risk sensitive, either for
trading or non-trading purposes. Therefore, TC PipeLines, LP is not exposed to
any interest rate risk, market price risk, or foreign exchange risk, except to
the extent that its 30% general partner interest in Northern Border Pipeline
exposes the Partnership to the market risks disclosed below.

Northern Border Pipeline's interest rate exposure results from its variable rate
borrowings from commercial banks. To mitigate potential fluctuations in interest
rates, Northern Border Pipeline maintains a significant portion of its debt
portfolio in fixed rate debt. Northern Border Pipeline also uses interest rate
swap agreements to manage the portion of its fixed rate debt. Since December 31,
1999, there has not been any material change to Northern Border Pipeline's
interest rate exposure.

                                      12

<PAGE>

                           PART II. OTHER INFORMATION

                                TC PIPELINES, LP

                    ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K

(a)   Exhibits.

      None.

(b)   Reports on Form 8-K

      None.

                                      13

<PAGE>

                                   SIGNATURES


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


                                 TC PIPELINES, LP
                                 (a Delaware Limited Partnership)

                                 By: TC PipeLines GP, Inc., its general partner

                                 By: /s/  Theresa Jang
                                    -------------------------------------------
Date:  May 12, 2000                  Theresa Jang
                                     Controller


                                      14