The purpose of this study is to provide an overall evaluation of the results and performance of the Global Environment Facility's (GEF) Climate Change Program from its inception in 1991 to mid-2004. The study will contribute to the third GEF Overall Performance Study and serves as a guide to future strategic directions. It draws on information gathered from a comprehensive portfolio review, greenhouse gas (GHG) emission data and development statistics, and two in-depth project cluster reviews within energy efficiency and renewable energy. The analysis was enhanced by several implementing agency reviews, other GEF monitoring and evaluation (M&E) reviews, and select country visits.