The suggested model for the alteration of the rocks from the Kremnica ore district and from the SW margin of the Kremnicke Vrchy Mts., is based on the existence of three mutually associated processes of different origins: the diagenetic alteration rhyolite tuffs, hydrothermal alteration of rhyolites and finally, hydrothermal alteration of andesites and rhyolite tuffs in the neighbourhood of the veins from the Kremnica ore district. Spatial coincidence in the mineral composition of rhyolites and rhyolite tuffs was confirmed in all the distinguished alteration processes. Polygenetic zoning mixed-layer illite/smectite + kaolinite, zeolites and smectite developed at the southern periphery of the Kremnica ore district in the direction from north to south. Hydrothermal alteration of the Kremnica ore zone belongs to the adularia-sericite type in the sense of Heald et al. (1987).