The digenetic trematodes described below were found in freshwater fishes collected near Kushiro, eastern Hokkaido, Japan. The fishes examined were fresh raw, frozen or formalinpreserved ones: 15 Hucho perryi (Salmonidae), 275 to 600 mm in fork length, from the Kushiro river water system (the Ashibetsu, Hororo, Kottaro, Kushiro, Ninishibetsu, Numahoro and Settsuri rivers) and the Bekanbeushi river water system (the Bekanbeushi and Toraibetsu rivers) during April 1966 to May 1977; 5 Salvelinus leucomaenis (Salmonidae), 270 to 540 mm in fork length, from the Ashibetsu and Numahoro rivers and a river belonging to the Kushiro river water system in April and May 1977; 7 Tribolodon hakonensis (Cyprinidae), not measured, from the Kushiro River near Toro in May 1977; 4 T. ezoe, 155 to 249 mm in fork length, from the Kushiro River near Toro in May 1977; and 2 Cottus nozawae (Cottidae), 139 to 146 mm in fork length, from the Ashibetsu River in May 1977.Most of the flukes obtained were flattened, fixed in ScHAUDINN′s solution or 70％ ethanol, stained with HEIDENHAIN′s iron hematoxylin or alum carmine, and mounted in Canada balsam. Some were mounted in balsam after being killed in hot 10％ formalin and stained with alum carmine. Serial paraffin sections were also made of some others and stained with hematoxylin and eosin. The parasite specimens delt with here are all deposited in the collection of the National Science Museum, Tokyo
