Many people argue that water resource development projects have negative health effects. In particular, they claim that an increase in schistosomiasis almost automatically results from building dams, irrigation systems, and other water-related activities in regions endemic for the disease. However, this literature review finds many cases where no such increase seems to occur. Some people explain this phenomenon by the adopting of preventive measures, such as providing adequate sanitary and water facilities and appropriate water management practices. Even when these are absent, there is often no increase in schistosomiasis transmission. Ecological variations in snail populations may be more important. Generalizations are usually misleading. For example, in Mali and northern Ghana, some studies associate small earthen dams with schistosomiasis transmission. But other studies from northern Cameroon, Burkina Faso, northern Nigeria, and northern Ghana did not find any transmission of schistosomiasis from impounding small bodies of water. In Asia, schistosomiasis occurs only with specific methods of rice cultivation in certain areas of China and the Philippines. In Africa, most evidence fails to show an association between irrigated rice cultivation and schistosomiasis. Water resources and agricultural development projects often receive unfair blame for creating health hazards such as schistosomiasis. The Aswan High Dam in Egypt is the most notable case. It might be prudent, however, for planners and policy makers to protect against possible increases in schistosomiasis transmission from water resource development projects. As part of project proposals, careful studies should be made of snail species and of existing patterns of schistosomiasis transmission. Further, a percentage of investment and operating funds should be allocated for appropriate water supply and sanitation and for health care to treat local populations for any water-related or other ailments associated with the project.