To date, guidelines specific to impact assessment of tropical dams have not been developed, particularly as regards hydrobiological and ecological impacts. The need for such guidelines motivated the Agency for International Development to commission the Smithsonian Institution's Office of International and Economic Programs to undertake a case study in Ghana of Volta Lake, formed by the Akosombo Dam on the Volta River. The purpose was to develop an empirical base of information from which guidelines could be evolved. This was one of three case studies undertaken. The other two studies addressed the environmental impact of rapid urbanization (Seoul, Korea) and the environmental impact of marine pollution by oil in the tropics (Indonesia). It is hoped that these guidelines will be useful for planners of future tropical dams, as well as for managers of existing dams, who are concerned with obtaining the best information possible on the potential environmental impacts of these important public investments. It is further hoped that these guidelines will be improved over time as our knowledge of the man-made lake ecosystem in the tropics increases.