A model for the economics of marine conservation is developed and tested using data from a global sample of Marine Protected Areas (MPAs). Results from logistic regressions indicate that significant determinants of positive MPA effects vary among MPA subgroups. These significant regressors include enforcement in later time periods and certain 鈥済oodwill building activities鈥?carried out by MPA management, as well as a number of institutional and socioeconomic characteristics of the communities. Policy implications and recommendations for additional research are discussed.