The Sheldon & Oswood (1977) model, that predicts a linear relationship between log filter-feeder density and log distance from a lake and assumes proportionality between filter-feeder density and seston concentration, was tested on data from four lake-outlet streams. In addition, longitudinal changes in species composition and body size in zooplankton were investigated. Most filter feeders deviated from the model and a quadratic, rather than linear, decrease in density was a common pattern. Total filter feeders and blackfly larvae showed a hump-shaped distribution pattern. Lower current velocity at sites close to lakes is suggested as an explanation. No general proportional relationship between net-spinning caddis larvae and zooplankton was found and several reasons for this result are discussed. Zooplankton biomass and mean zooplankton body length decreased with distance from lakes. The abundance of cyclopoid adults, copepodites, and nauplii declined at a higher rate than Bosmina spp. This result indicates that factors such as selective predation by filter-feeders and/or taxon-specific sedimentation rates, are acting to reduce zooplankton abundance in these lake-outlet streams.