In this paper we assess the institutional and environmental impacts of forest decentralization in Bolivia, Kenya, Mexico, and Uganda. We develop theories of institutional impacts based upon the specific content of decentralization reforms. We classify each country's reforms in terms of the creation/change in local user group empowerment and accountability mechanisms. Using data from the International Forestry Resources and Institutions Program, we estimate the effects of forest decentralization on local forest investments, rulemaking, wealth inequality, and forest conditions in the four countries. Some results support our theory, but the theory is insufficient to explain the full range of outcomes.