During the period May-October 1991 a hydrochemical investigation was carried out in the Waksmundzka Valley lying on the granite substratum of the High Tatra Mountains. An acidification of the Waksmundzki Stream dependent on precipitation was observed in spring, while heavy late summer and autumn rainfall reduced the quantity of the acidic substances. Differences in the stream chemistry between the upper and lower part of the catchment were also observed. The small amount of groundwater entering the lower part of the stream is believed to be responsible for it.