The object of this thesis is the assessment of fish contamination by selected foreign substances as toxic metals, polychlorinated biphenyls and pesticides in 31 selected fishing grounds. The monitoring was realized between years 2006 and 2010. Fish were caught by electric device and fishing rods. Concentrations of Hg, Cd, Pb, PCB, DDT, HCH and HCB in fish muscle tissues were monitored. Common bream (Abramis brama) was selected as a reference species for a comparison of the monitored sites. The results of analysis were compared with valid hygienic limits. Overrun of hygienic limit for some of the monitored pollutants were observed in 18 localities. We found mercury as a major pollutant in the aquatic environment.