The investigation of polychaete fauna in 3 brackish-water lakes located in Shimane Prefecture, Japan, were conducted from 1992 to 1993, to clarify species composition, community structure and lake-specific characters. Polychaete community is richest in Lake Nakaumi, which also shows the most saline environment among the 3 lakes. Other 2 lakes, Lake Shinji and Lake Jinzai, possess poor polychaete fauna, and monopolistic community structure. The most abundant species in deeper mud in 3 lakes belong to family Spionidae, and among them is Paraprionospio pinnata, its presence indicates orgainc pollution. Lakespecific characters of polychaete commuinties and their relation to salinity and bottom sediment are discussed.