Groundwater sampling was carried out between July 2014 and January 2017, from four wells in the district of Topoľčany, Preseľany and Veľké Bedzany, which belong to vulnerable areas. The aim of the research was to detect nitrate concentrations in selected water samples in selected wells and to determine the suitability of their use as drinking water sources. The results of the analyzes allowed to evaluate changes in their concentrations during different seasons. In the Preseľany village NO3- concentration during the monitored period in well no. 1 ranged from 128.47 to 215.40 mg.l-1 and no. 2 from 116.07 to 215.96 mg.l-1. In the village of Veľké Bedzany in well no. 3 from 46.07 to 100.46 mg.l-1 and no. 4 from 56.70 to 110.96 mg.l-1. Compared with the limit value (50 mg.l-1) specified in the Government Regulation no. 496/2010 Coll., higher concentrations of nitrates were found in all water samples taken during the monitored period. An exception was only the well no. 3 in the village Veľké Bedzany, where their lower concentration was measured in the summer (July, 2015). Based on the results obtained, the wells were recommended not to use the well water for drinking purposes.