Macrozoobenthic samples of two North Patagonian river basins, Negro (Argentina) and Valdivia (Chile) were taken in the period 1977-1983 in order to compare habitats of aquatic insects and other invertebrates on both slopes of the Andes and at the same latitude. Ten genera of Plecoptera were recorded by the author as nymphs: Gripopterygidae (Antarctoperla, Limnoperla, Potamoperla, Pelurgoperla , and Araucanioperla ?), Diamphipnoidae (Diamphipnoa and Diamphipnopsis ), Austroperlidae (Klapopteryx ), Notonemouridae (Austronemoura ) and Perlidae (Kempnyella ). Most of these genera of Plecoptera were collected in the upper rhithral. Only Antarctoperla and Limnoperla were found in reservoirs, in one lake and in medium-size to wide rivers. Gripoperygids were more frequent on the Argentine side; the other families were more abundant on the opposite slope; this situation can probably be explained by the different ecological conditions brought about by cattle raising and dam construction.