ABSTRACT: Mass flux (MF) balance of dissolved contaminants was evaluated at two mountain mine sites in Slovakia, using hydrometric measurements of streams and mine water outflows, and laboratory analysis of water samples. The results show that chemical weathering of the minerals at the Dubrava Sb deposit located in the crystalline basement of the Low Tatras Mts. releases about 2.8 t·y-1 of Sb that is washed away by the Paludžanka stream. As much as 2.0 t·y-1 of Sb is in mine waters from 6 adits, suggesting that cleaning of these mine water sources could significantly reduce Sb concentration in the Paludzanka stream water. At the Slovinky Cu deposit located in the Paleosoic metamorphites of the Slovak Ore Mts, the Slovinsky stream carries away about 1.6 t·y-1, 0.34 t·y-1 and 0.14 t·y-1 of Mn, As and Sb, respectively. At that locality, the Alžbeta adit, together with drainage systems of two settling pits, releases 2.1 t·y-1 of Mn, 0.19 t·y-1 of As and 0.01 t·y-1 of Sb dissolved in water. This suggests that considerable amounts of Mn precipitate from solution and almost all the Sb comes from different, currently unknown sources. Cleaning mine and drainage waters at Slovinky deposit could significantly reduce both the Mn and As concentrations in the Slovinsky stream, but not the concentration of Sb. Although these presented results of MF calculations are preliminary, they suggest a very successful application of this method in the assessment of contaminated mine sites and for prognosis of remediation effectiveness.