This report presents the assessment of Lakes Turkana, Tanganyika, Victoria and Malawi, the largest of the East African Rift Valley Lakes and among the oldest lakes in the world. The lakes are renowned for their high endemism and support a vital socio-economic service as a core for transportation, water supply, fisheries, recreation and tourism. Anthropogenic impacts have significantly altered the ecosystem function of these lakes. Lake Victoria, shared by three countries and influenced by two more in the catchment area, was targeted for causal chain and policy option analysis. Root causes related to pollution and overexploitation are discussed and policy options to address the driving issues are presented.--Publisher's description.