The vertical and horizontal distribution of Copepoda and Cladocera in Tjeukemeer were studied. Indices of dispersion are discussed, the sample variance of log-transformed data proved to be an appropriate way to quantify patchiness. Indices of dispersion were calculated to express species specific differences. Only during short periods of the year the population densities appeared to be influenced by canals and pumping stations that bring water to the lake. Dispersion values were influenced by windspeed, inhomogenities in the chlorophyll-a concentrations and by the population densities of the populations studied. Sample variances are relatively low, compared with those of other lakes.