This article explores the proposed multibillion dollar Trans-ASEAN Gas Pipeline (TAGP) network in Southeast Asia, focusing on the interests that have promoted the TAGP and why. Based on extensive field research, textual analysis of government reports, and more than 100 research interviews at government institutions, multilateral development banks, universities, consulting firms, energy companies, and nongovernmental organizations, this article assesses the challenges facing the TAGP in terms of promotion, implementation, and operation. It explores the genesis of the TAGP project and the drivers pushing Southeast Asian investment in natural gas, with a special emphasis on the development needs of the region. It also investigates the numerous technical, economic, legal, political, social, and environmental impediments to the TAGP project. The article concludes that the rhetoric of regional energy cooperation touted by the Association of Southeast Asian Nations (ASEAN) does not match its actual practice, and that in many cases discussions of regionalism and energy security are intended to obscure opportunistic thinking within individual countries. (C) 2009 Elsevier Ltd. All rights reserved.