Our study presents the hydrochemical data obtained from seven perennial springs located on the Jasov Plateau – Slovak Karst. It is part of the most heavily karstified area in Slovakia extending into northern Hungary. Monthly observations of discharge, temperature and the calcium content have been carried out on perennial springs for 19 months. Since November 2013 the seasonal changes of the basic hydrochemical parameters (water temperature, electric conductivity, pH and major ions), the stable isotope composition and tritium content have been measured on a regular basis. Except for water temperature, no other parameter showed a clear seasonal signal. Statistically significant relationships were discovered between some springs concerning the fluctuation of the various parameters. The stable isotope analyses of the water samples showed that the springs are of meteoric origin, their stable isotope composition varied between -74.9‰ to -62.1‰ and from -10.5‰ to -9.5‰ for δD and δ18O, respectively. The mean residence time of the water varies between 3.5 and 6 years (tritium concentration).