1 EXHIBIT 21.1 SUBSIDIARIES PERCENT PLACE OF OWNERSHIP INCORPORATION CMS Oil and Gas Company Michigan CMS Oil and Gas (International) Ltd. 100% Cayman Islands CMS Oil and Gas (Alba) LDC 100% Cayman Islands CMS Oil and Gas (Argentina) LDC 100% Cayman Islands CMS Oil and Gas (E.G.) LDC 100% Cayman Islands Alba Associates LLC (partial interest owned by CMS Oil and Gas (Alba) LDC, CMS Oil and Gas (E.G.) LDC and CMS Oil 54% Cayman Islands and Gas (E.G.) Ltd.) Alba Plant LLC 80% Cayman Islands Punta Europa LLC (50% owned by CMS Oil and Gas (Alba) 100% Cayman Islands LDC and 50% owned by CMS Oil and Gas (E.G.) LDC) CMS Oil and Gas (E.G.) Ltd. 100% Cayman Islands CMS Oil and Gas (Congo) Ltd. 100% Cayman Islands CMS Oil and Gas (Venezuela) LDC 100% Cayman Islands CMS Oil and Gas (International) Company 100% Texas CMS NOMECO International Congo Holdings, Inc. 100% Texas CMS NOMECO Congo, Inc. 100% Delaware CMS Oil and Gas (Cameroon) Ltd. 100% Cayman Islands CMS Oil and Gas (Cote d'Ivoire) Ltd. 100% Cayman Islands CMS Oil and Gas (Eritrea) Ltd. 100% Cayman Islands CMS Oil and Gas (Services) Company 100% Texas CMS Oil and Gas International (Tunisia) Company 100% Texas CMS Oil and Gas (Pipeline) Company 100% Michigan Explotaciones CMS Oil and Gas Company 100% Delaware NOMECO Ecuador Oil Company 100% Michigan