Our study is aimed at microbiological analysis of water samples originating from a small municipal lake in Szczecin, called Syrenie Stawy. The studies were conducted for a year in monthly intervals. The variables estimated in the water samples included the extent of contamination (TVC 20^oC and TVC 37^oC), content of sanitary status bacteria (coli group bacteria, TC), foecal-type coli group bacteria (FC), foecal streptococci (FS) and bacteria of physiological types (denitrification, amonification, sulphate- and sulphite-reducing bacteria). Results of the studies demonstrated high content of sanitary bacteria, which pointed to a significant contamination of the lake. High content of psychrophilic and mesophilic bacteria pointed to high amounts of organic substances in water. On the other hand, the high content of NPL, of coli group bacteria titres and of foecal type coli group bacteria provided evidence for drainage of communal sewage to waters of Syrenie Stawy. This was additionally proven by the presence of foecal streptococci. As far as physiological bacteria were concerned, the extensive differences in between mean values obtained for various sampling points may indicate unequal loading of Syrenie Stawy waters with contaminants in various points of their coastal zone.