This article analyzes the political influence of business in the context of international environmental cooperation. Locating the sources of business power in three distinct factors—organizational strength, structural privilege, and informational advantage—the article evaluates the contributions of these factors to explanations of states' ratification of, and compliance with, international environmental agreements. Using data on 35 advanced industrialized democracies, the results suggest that business influence can be best explained by reference to informational asymmetries. While countries whose economies are exposed to international trade tend to participate less in international regimes, strong domestic environmental movements can counteract incentives for non-participation by providing political decision-makers with alternative information about the costs and benefits of participation. Regime compliance also increases with the availability of independent information through environmental groups, as well as with the degree of politico-economic integration found in neocorporatist systems of interest intermediation.