The growing concern of the international community over effective modes of international governance after the Cold War has been accompanied by a lively academic interest in regime theories. In contrast to the 1980s and early 1990s, scholars are now less interested in explaining the generation and maintenance of regimes than in their impact on international co-operation and their contribution to solving urgent problems. Environmental issues in particular, whether global or regional, have proven fertile ground for institutionalist theories, particularly for developing concepts and testing propositions regarding the determinants of implementation, compliance, and effectiveness of international regimes. Yet although the notion of regime has acquired great pre-eminence in international environmental politics and the study of regimes has become a prolific industry, uncertainties abound about the concept itself.