This paper evaluates contamination and sanitary and bacteriological states of the waters in the Czarna Hancza River in the region of Suwalki and Wigry National Park, and treated wastes coming from an urban sewage treatment plant. Microbiological examinations were carried out every month, in three annual cycles, in 1994-1996. Water samples were taken at 11 stations situated in the most characteristic places above Suwalki, below Suwalki, before inflow of treated wastes coming from the sewage treatment plant, in Sobolewo and at the mouth of the Czarna Hancza River to Wigry Lake, besides the tract from Czerwony Folwark to Wysoki Most towards the east of Wigry Lake. The following microbiological indices were examined: TVC 20^oC, TVC 37^oC, TC, FC, FS, Clostridium perfringens as well as numerical ratio FC:FS. The results of the examination of the number of respective indicator bacteria were compared with the purity criteria, organic substance loading and excrement material and water usefulness for recreation. Unsignificant contamination of the Czarna Hancza River was observed in Stary Brod not far from Suwalki and in Czerwony Folwark, Mackowa Ruda and Buda Ruska in the eastern part of Lake Wigry, significant and/or strong water contamination of this river was noticed on the track from Suwalki to its mouth to Wigry Lake. The sources of the contamination were shown: point (sewages) and spacious (catchment) and leakage from cesspools in Sobolewo. A significant decrease of the number of the examined indicator bacteria of the contamination degree (TVC 20^oC, TVC 37^oC) of this part of the river in 1995 and 1996 was observed. The usefulness for bathing the examined fragment of the River Czarna Hancza above Suwalki and the fragment from Czerwony Folwark to Wysoki Most towards the east from Wigry Lake was presented.