Three alteration zones are recognized in hydrothermally altered granitoid rocks at the Dubrava Sb-Au deposit, Nizke Tatry Mts., Western Carpathians: the outermost chlorite zone, muscovite zone and the innermost illite-carbonate zone. Chlorite replacing biotite originated at temperature about 320 ± 40 °C (according to Cathelineau 1988) and the frequency distribution of Al^IV in chlorite suggests its re-equilibration during later hydrothermal events. The muscovite and illite-carbonate zones are superimposed on the chlorite zone. Muscovite appears to be of both magmatic and hydrothermal origin, as deciphered from its TiO₂ content. Hydrothermal muscovite replaces plagioclase and chlorite. In the innermost zone, carbonates and sulphides become abundant, muscovite and feldspars are replaced by illite. Measurements of crystallinity index values of illite gave an estimate of 180–200 °C for the illite-carbonate zone. The altered rocks were enriched in K₂O, H₂O, CO₂, Sb and S and depleted in CaO, MgO, Fe₂O₃, and Na₂O. Minor changes in Al₂O₃ and SiO₂ content are ascribed either to the variations of the composition of the primary magmatic precursor or local redistribution of these elements. Limited data on alteration of amphibole gneisses and migmatites suggest that the main processes were chloritization and illititation; SiO₂ and Na₂O were removed and K₂O added to these rocks.