TransCanada to Increase Interest in Portland Natural Gas Transmission.

Business Editors

CALGARY, Alberta--(BUSINESS WIRE)--Sept. 23, 2003

TransCanada Corporation (NYSE: TRP)(TSX: TRP) today announced that it has exercised its right to increase its ownership interest in Portland Natural Gas Transmission System (PNGTS) to 43.42 per cent, an increase of 10.13 per cent. TransCanada will increase its interest by acquiring a portion of DTE East Coast Pipeline Company's interest in PNGTS for approximately US$47.1 million, including assumed debt of approximately US$27.8 million.

The transaction is expected to close within the next month. Upon closing, ownership of PNGTS will be: TransCanada (43.42 per cent); El Paso Corporation (29.64 per cent); and Gaz Metropolitain and Company, Limited Partnership (26.94 per cent).

PNGTS operates a 471 kilometre, 220 million cubic feet per day interstate natural gas pipeline which connects with the Trans-Quebec & Maritimes Pipeline near Pittsburg, New Hampshire and has delivery points in Maine, New Hampshire and Massachusetts, including the Boston area.

TransCanada is a leading North American energy company. We are focused on natural gas transmission and power services with employees who are expert in these businesses. Our network of approximately 38,000 kilometres (24,000 miles) of pipeline transports the majority of Western Canada's natural gas production to the fastest growing markets in Canada and the United States. TransCanada owns, controls or is constructing more than 4,500 megawatts of power - an equal amount of power can meet the needs of about 4.5 million average households. Our common shares trade under the symbol TRP on the Toronto and New York stock exchanges. Visit us on the Internet at www.transcanada.com for more information.

FORWARD LOOKING INFORMATION

Certain information in this news release is forward-looking and is subject to important risks and uncertainties. The results or events predicted in this information may differ from actual results or events. Factors which could cause actual results or events to differ materially from current expectations include, among other things, the ability of TransCanada to successfully implement its strategic initiatives and whether such strategic initiatives will yield the expected benefits, the availability and price of energy commodities, regulatory decisions, competitive factors in the pipeline and power industry sectors, and the current economic conditions in North America. For additional information on these and other factors, see the reports filed by TransCanada with Canadian securities regulators and with the United States Securities and Exchange Commission. TransCanada disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.