The objective of the study was to check the health status of the anadromic river lamprey Lampetra fluviatilis (L.), the most frequently recorded lamprey species in Poland caught in Lake Dabie, connected with the Odra river estuary. The species composition of parasitofauna of the river lamprey from the Polish waters was compared to the pathogens of this host noted so far. The skin and fins, eyes, oral cavity and nasal mucus of 36 lamprey specimens were examined. After decapitation the brains and gills were analysed. A single gonad, liver and the kidney wet microscopic preparations were made and examined. Examination was also made of the contents of the straight alimentary tract, the body cavity and muscles from the dorsal area. The pathogens known of the river lamprey are mostly the parasites of a very low extensity. No monogeneans were found among the parasites recorded. The reasons of such species composition of the parasitic fauna are discussed against the background of the anatomy, physiology and biology of the host. In the alimentary tract of one lamprey single larva of the nematode Anisakis simplex (Rudolphi, 1809) was found, not noted yet in this host in Poland and Europe. The parasite was noted in any of the lamprey species occurring in neither fresh nor saline waters in Europe. Such a low prevalence and intensity of the infection pointed that this nematode as many other species of parasites was swallowed accidentally.