The morphology of types F, A, C plerocercoids, and mature Diphyllobothriidae of the Far Eastern populations (USSR) was studied by using scanning electron microscopy. New data were obtained on structure the skin muscular sac of plerocercoids type F (presence of tegumental microvilli, multi poly-layer of longitudinal subtegumental musculature, and variation of quantity of muscular filaments along strobila. The morphological identity of mature Diphyllobothriidae from the volunteer (self-infection of plerocercoid "type F"), infested men and seagulls from focuses of diphyllobothriasis in the Pacific Ocean regions in the Far East of the USSR was proved.