This thesis provides an assessment of slope stability on the main dam of the upper reservoir at the pumping water plant Ipeľ. Information about geological conditions and geometrical disposition were taken from archive materials from HYDROPROJEKT Brno (1989). Both, upstream and downstream slopes were assessed in six load states: post building-up phase without water in the reservoir, state with minimal and maximal water level in the reservoir, a sudden fall of water level state, additional traffic load on the dam crest and action of seismic activity. Geotechnical calculations were performed in modelling program GEO5 (STABILITY module). Factors of safety (FOS) were calculated according to Petterson, Bishop and Sarma and compared with the required values in Slovak technical norm STN 73 6850.