AbstractDuring complex ecological investigations on Lake Jarun (and neighbouring interstitial underground waters) which took place in 1984 and 1985, macrozoobenthos was also studied. Its qualitative and quantitative composition in a large part depends on the degree of trophy and saprobity of the water. Specially examined were the oligochaetes and chironomids larvae, which besides having a large numerical percentage also occurred with a large number of species. In addition, the representatives of other groups of macroscopic invertebrates were also mentioned, especially those which have a special significance as indicators of a certain degree of trophy and saprobity, and which are important because of their oasis preservation in this ecosystem.