Scholars and practitioners have paid considerable attention to the factors that promote successful outcomes in environmentally focused assistance projects. Previous studies have identified various potential predictors of successful outcomes, including the political commitment, institutional capacity, and governance quality of the recipient country; the severity of environmental pressures in the recipient country; donor-recipient contracting dynamics; project characteristics; and civic participation in the recipient country environment sector. We test the influence of these variables on project success using a dataset of outcome ratings for all environmentally focused World Bank projects approved since 1994. We find that strong public sector institutions in the recipient country and proactive staff supervision foster project success and that projects seeking to achieve global environmental objectives are less likely to succeed. Future research will be most fruitful if it focuses on how operational and management characteristics of individual projects lead to successful outcomes.