This bachelor thesis, entitled Evaluation of Pollution of a Selected Surface Stream, is concerned with surface water quality. We concentrated our efforts on the Detviansky stream because it was suspected of being polluted and showed signs of eutrophication. By analyzing the samples, we were able to determine the basic parameters of water quality. The indicators of water quality chosen were primarily nitrates and the presence of total phosphorus in the water. The measured findings were compared to the upper and lower limits set in Government Decree no. 269/2010 Coll.