Presents results of an inquiry into the effects of water projects on the transmission schistosomiasis. a parasitic disease, involving both human and snail hosts. The report describes the study's final stage, in which a previously developed schistosomiasis transmission model was tested using new field data related to small water projects in Tanzania. The study focuses primarily on the impact of changes in water availability on human contact with snail habitats, measures of infection in the human population, and the cost-effectiveness of data collection methods. In addition, the role of human migration in disease transmission is examined. After describing the basic model and reviewing the incidence and control of schistosomiasis in Tanzania, the report details modifications made with new Tanzanian data on the original model and provides model-related epidemiological analyses. Next, a cost-effectiveness analysis is performed for schistosomiasis control measures. These two analyses (epidemiological and economic) are subsequently combined to form a predictive methodology for use in project evaluation. Recommendations are made regarding future research.