Parasite fauna of the bullhead Cottus kolymensis in the rivers Penzhina and Talovka is considered for the first time. In total, 19 species of parasites are found, including two speciesspecific ones: Echinorhynchus cotti (marine) and Trichodina tumefaciens (freshwater). Boreal lowland species prevail (9) among the parasites, infusoria have the highest species diversity (7 species). Invasion of parasites typical for mass fish species, as ninespine stickleback, northern pike, burbot, and salmons, is detected. The environments favorable for the bullhead parasites are characterized by plenty organics, active mixing of bottom sediments, and abundant benthos that is favorite prey for this fish species. [ABSTRACT FROM AUTHOR]