The aim of this paper was to describe the oligochaete fauna from underwater hydrothermal vent affected zone of the Frolikha Bay (Northern Baikal), where the group is dominated in zoobenthic communities. The paper provides information about a unique community of oligochaetes inhabiting here. Uncharacteristic for the abyssal zone of Lake Baikal high indices of oligochaete development were revealed. Possible dependence of species composition and quantitative characteristics of oligochaetes on the development of bacteria Thioploca in the area were analyzed.