The eastern-European tundra is regarded as a classic example of European plain tundra. There are many lakes in the region, particularly small thermokarst lakes in the eastern Bolshezemelskaya tundra. However, studies on biodiversity of the waters of this Russian tundra have never included mycological research. Fungi on submerged fallen leaves and dead larger plants were therefore studied in five expeditions from July, 1993 to August, 1996. Small lakes were observed in the Vorkuta tundra, in relatively clean areas and in areas subject to human disturbance. Thermokarst lakes near Mulda were relatively clean. A total of 18 taxa (species and varieties) of aquatic hyphomycetes, 2 of aero-aquatic hyphomycetes and 4 of terrestrial/aquatic discomycetes were collected on plant substrata. Other ascomycetes and coelomycetes were also found on submerged substrata. Another group of relatively clean lakes was situated to the south-east of Vorkuta in the region of the Usa river. In these peat lakes with acid water, 11 species of aquatic and 3 aero-aquatic hyphomycetes were recorded on plant substrata, as well as 5 species of ascomycetes and coelomycetes on submerged substrata. The remaining lakes were in areas disturbed by various human activities. The fungi most sensitive to the pollution are aquatic hyphomycetes. Only 4 species were found in lakes in areas polluted by cement works. In lakes polluted by concentrated coal and coal-dust, 7 species were collected; in lakes polluted by domestic and industrial waste near Vorgashor village, 5 species of aquatic hyphomycetes were recorded. The occurrence and abundance of fungi in all these lakes were rather low. Aero-aquatic hyphomycetes and terrestrial/aquatic discomycetes were more stable in the presence of pollution. Where human pressure is highest on fungi in the lakes near Vorgashor, the result is the vanishing of specialist aquatic species and their replacement by ubiquitous non-specialist hyphomycetes.