In the Rożnów Reservoir the taxonomic composition of benthic insect larvae assemblages became distinctly poorer. Among midges the genus Procladius still dominated with a usually small participation of Chironomini and other subgroups. In the polluted River Dunajec above and below the reservoir larvae of the genus Cricotopus (Orthocladiinae) occurred in the greatest numbers. In the Czchów Reservoir, its tributary Łososina, and in the Dunajec below the dam the insect fauna was more diverse, particularly Chironomidae, Ephemeroptera, and Trichoptera. The structure of the benthos assemblages chiefly depended upon the kind of bottom, the current velocity, and the physico-chemical parameters of the water.