[en] The trichopterological research was conducted in six localities of the Cierny Vah river and one locality in the Vah river, not far from the confluence of the Biely Vah and the Cierny Vah rivers. The upper part of the Cierny Vah river represents an undisturbed section, which was examined in four localities. After this section, the river is impacted by the pumped-storage hydropower plant Cierny Vah. Cluster analysis (Ward's method) separated two below-dam localities from other metarhithral localities. The last locality belonged to the unimpacted group, which signalised renaturalization of the river. The dominant species of the unimpacted section was Ecclisopteryx dalecarlica while the below-dam section was dominated by a tolerant genus Hydropsyche. (authors)