In article are presented the results of the state of the pelagic part of the south stretch of Lake Munozero (Karelia) according to microbiological indicators for the growing season of 2018. In the furtherance of this goal, 27 water samples were chosen in May, July and September at different strata. Munozero Lake is one of the unique lakes of Karelia due to its high salinity (100 mg/l), low-nutrient water sand organic substances. The total number, cell size dimensional structure and biomass of bacteria were determination by method of luminescence microscopy, by means of filtration through black nucleopore track membranes, after coloration bacteria by acridine orange. The total abundance of bacteria varied from 0,66 to 1,85 million cells/ml, and the biomass from 0,13 to 0,66 g/m3. The average cell volume varied in the range 0,18-0,34 μm3. Coccus form of bacteria prevailed in numbers. The doubling time and bacterial production were determined by the method of isolated samples. Bacterial production varied between 0,01 and 0,07 g/(m3•day-1). Specific growth rates (day-1) ranged around 0,05-0,2, giving doubling times of 70-364 h. The average daily production for the growing season was 0,65 g/m3•day-1. The physiological activity of bacteria was greatest at the end of the growing season. During the research period, the abundance of saprophytic bacteria growing on fish peptone agar was in the range of 19-550 CFU/ml. the abundance of oligotrophic bacteria growing on from starvation agar variable 200 to 850 CFU/ml. During the study period Water of the south stretch of the Lake Munozero was estimated as clean - moderately polluted with an intermediate quality class of 2-3. The south stretch of the Munozero is characterized as a mesotrophic water body.