EXHIBIT 21 SUBSIDIARIES OF NGC CORPORATION STATE OR JURISDICTION OF INCORPORATION NAME OF SUBSIDIARY OR ORGANIZATION - ------------------ --------------------- Accord Energy Limited United Kingdom Bradshaw Gathering System Joint Venture Texas Caney River Transmission Company Delaware Clearinghouse Holdings, Inc. Delaware ECI Capital Corporation Texas Electric Clearinghouse, Inc. Texas Ellisburg Leidy N.E. Hub (general partnership) Pennsylvania Enerchange LLC (limited liability company) Delaware Gulf Coast Fractionators (general partnership) Texas Hub Services, Inc. Delaware Kansas Gas Supply Corporation Delaware LPG Services Group, Inc. Missouri Natural Gas Clearinghouse (general partnership) Colorado Natural Gas Clearinghouse, Inc. Delaware Natural Gas Clearinghouse of Argentina, Inc. Delaware Natural Gas Clearinghouse of Mexico, Inc. Delaware NGC Anadarko Gathering Systems, Inc. Texas NGC Avoca, Inc. Delaware NGC Great Britain Ltd. United Kingdom STATE OR JURISDICTION OF INCORPORATION NAME OF SUBSIDIARY OR ORGANIZATION - ------------------ --------------------- NGC Canada, Inc. Alberta, Canada NGC Cayuta, Inc. Delaware NGC Futures, Inc. Texas NGC GP, Inc. Delaware NGC Global Energy, Inc. Delaware NGC Global Liquids, Inc. Delaware NGC Holding Company, Inc. Delaware NGC Mexico, S.A. de C.V. Mexico NGC Oil Trading and Transportation, Inc. Texas NGC Regulated Holdings, Inc. Delaware NGC Steuben, Inc. Delaware NGC Storage, Inc. Delaware NGC Transportation, Inc. Delaware NGC UK Limited United Kingdom NIPC, Inc. Texas NOTTI Gathering Company, Inc. Delaware NOTTI Pipeline Company Delaware Novagas Clearinghouse Limited Partnership Alberta, Canada (limited partnership) O'Keene Gas Gathering Company Oklahoma Ozark Pipeline, Inc. Delaware 2 STATE OR JURISDICTION OF INCORPORATION NAME OF SUBSIDIARY OR ORGANIZATION - ------------------ --------------------- Phantex Pipeline Company Delaware QuickTrade LLC (limited liability company) Delaware Warren Arkansas Gathering, Inc. Arkansas Warren Energy, Inc. Texas Warren Energy Resources, Limited Partnership Delaware (limited partnership) Warren Gas Liquids, Inc. Delaware Warren Gas Marketing, Inc. Delaware Warren Intrastate Gas Supply, Inc. Delaware Warren NGL, Inc. Delaware Warren NGL Pipeline Company Delaware Warren Petroleum Company, Limited Partnership Delaware Warren Petroleum G.P., Inc. Delaware Warren Transportation, Inc. Delaware WPC LP, Inc. Delaware WTLPS, Inc. Delaware Waskom Gas Processing Company (general partnership) Texas 701289 Alberta Ltd. Alberta, Canada 3