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                                                                    EXHIBIT 21.1


                         SUBSIDIARIES OF THE REGISTRANT


1.   The Registrant holds a 98.9899% limited partner interest in TC PipeLines
     Intermediate Limited Partnership.

2.   Through its interest in TC PipeLines Intermediate Limited Partnership, the
     Registrant holds a 30% general partner interest in Northern Border Pipeline
     Company.

3.   The Registrant holds a 98.9899% limited partner interest in TC Tuscarora
     Intermediate Limited Partnership.

4.   Through its interest in TC Tuscarora Intermediate Limited Partnership, the
     Registrant holds a 49% general partner interest in Tuscarora Gas
     Transmission Company.