ABSTRACT: The basis for assessing the quality and chemical composition of groundwater was to gather and evaluate the results of chemical analysis in 2009th. From archival sources, we used analysis of y. 1962 to 1965). The main source are the chemical analysis in the solution of problem Žiarska Neogene Basin - hydrogeological region N 087 (period 2006 – 2007) and data from the hydrogeological and hydrogeochemical mapping in the years 2007 to 2009. Almost 50 year span analysis of some water sources (allow us to assess the change in chemical composition of water, but mainly by the quality of their representation of selected chemical elements (As, Al) and nitrates. The chemical composition of water presents a variety of rock environment of groundwater circulation. In the basin dominant representation are the components Ca-HCO3 and Ca-(Mg)-HCO3, proportional representation of other components is lower. Groundwater quaternary deluvial-proluvial sediments, respectively fluvial sediments of river terraces are characterized the highest content of dissolved substances. Type A2 is dominated in the basin, type A1 occurs in the southwestern part of Žiarska kotlina basin. Žiarska kotlina basin belongs among the most vulnerable areas. Contamination was demonstrated mainly in the southwestern and northwestern part of Žiarska kotlina basin. The main contaminants are Fe, Mn, As, and Al. This pollution is likely to originate in the agricultural and industrial activities.