The article presents an analysis of the epidemic situation in the priority parasitosis of the population in the Sakha Republic. The research shows the influence of sanitaryparasitological contamination of surface water sources with propagative forms of pathogens of diphyllobothriosis, enterobiosis and ascaridosis on the helminthiases morbidity among the population. Water contamination of the Sakha water pools by municipal sewage waste, discharges of river vessels during the navigation period, invasiveness of fish by plero-cercoids of diphylobothriids, contamination of the population with diphyllobothriosis followed by contamination with eggs of diphyllobothriids of domestic sewage, – all the mentioned facts reveal circulation of the pathogen and confirm the presence of diphyllobothriosis in middle flow of the Lena river in the borders of the city of Yakutsk. The influence is exerted by the dissemination of communal sewage and, consequently, of surface water sources by the propagative forms of biohelminths on the epidemic disadvantage of the Yakutia population with diphyllobothriosis. Diphyllobothriosis is the dominant biogelmintosis in the region. The high level of enterobiosis (contact helminthiasis) infectiousness among the population and an insignificant incidence of ascaridosis (typical geogelmintosis), in our opinion, is due to sanitary and hygienic living conditions of the population and climatic and geographic features of the region.