Benthic macroinvertebrates are sensitive to any kind of changes in the aquatic environment. The distribution, taxonomic composition and relative abundance of benthic invertebrates are strongly affected by the availability and quality of feeding resource, sediment type, substrate and water quality. For this reasons benthic macroinvertebrates traditionally served as reliable bioindicators to detect and identify changes in water systems. The aim of the proposed study was to analyze taxonomic composition of the Tbilisi water reservoir littoral benthic macroinvertebrates and their relationship with chemical characteristics of water. Tbilisi water reservoir (Tbilisi Sea) is located in the northern part of Tbilisi – N 41.75, E 44.85. Surface area is 11.6km2, maximum depth – 43 m, average depth – 26.6 m, water volume - 300 million m3. Filling of the reservoir started in 1951 by 11-km channel from the Iori River. Initially the reservoir was supplied only from Iori River. With time, the water level decreased significantly and its filling became possible only in 80-ies, after launching of Zhinvali Hydropower plant (N 42.09, E 44.45). Currently Tbilisi water reservoir is fed from the Iori River and mostly from the Aragvi River. Before filling the reservoir, there were three shallow saline lakes: Avchala (Kukia), Ilguniani and Avlabari lakes. 6 main benthic groups were determined during the research (2008, 2009): Oligochaeta, Ostracoda, Amphipoda, Chironimidae (Diptera), Ephemeroptera, Trichoptera, represented by different amounts depending on seasons. Presently the biomass of the benthic groups show drastic decline. Among collected zoo material only Oligochaeta representatives were identified to the species level: 9 species were described. Correlation between these species and organic pollution was analyzed. Positive correlation with the organic pollution was detected in three cases: with Nais psaudobtusa, Vejdovskyella intermediateand Chaetogaster Langi. These 3 species were not recorded in the Tbilisi Water Reservoir in 1964. Negative correlation with the organic pollution was identified in five cases: Dero obtusa, Uncinais uncinata, Amphichaeta leydigi, Limnodrilushoffmeisteri, Aulodrilus pluriseta. None of them was detected in the samples after increase of permanganate oxidation and COD, although all five were detected in 1964. Comparison of the current results of complex hydrochemical and hydrobiological studies with the results of the similar studies carried out 40 years ago revealed eutrophication process in the reservoir.