Taxonomic composition, distribution, community structure and seasonality of Lake Naivasha zooplankton between 1978 and 1980 are described. The ecological status of the zooplankton in relation to prevailing ecological factors and the lakes fishery are discussed. Species composition of the zooplankton community in Lake Naivasha has been remarkably constant since first observations between 1929 and 1931. The community structure and distribution of the zooplankton in the lake varied little from July 1978 to July 1980, however, there was evidence of species succession among the larger zooplankters, especially the cladocerans. In the littoral area zooplankton contribute significantly to the food and production of juvenile fish. There is an absence of fish zooplanktivores in the limnetic area of the lake. Consequently the limnetic zooplankton is not utilised by higher trophic levels.