An investigation on the helminths of wild animals (Martes melampus, Meles meles, Mustela sivirica, Myocastor coypus, Nyctereutes procyonoides and Vulpes vulpes) caught in the systems of the Chugoku mountains of Hiroshima and Okayama prefectures was done from December in 1970 to October in 1974. The worms, genus Concinnum, were found from the pancreatic duct of Nyctereutes procyonoides, Martes melampus, Meles meles and Mustela sivirica. The parasitic rate of Concinnum in Martes melampus is 100 % (the average number of parasites is about 3000), in Nyctereutes procyonoides 23.8% (40), in Mustela sibirica 20% (225) and in Meles meles 50% (9). The parasites were fixed with Schaudin's solution while compressed between slide glasses, stained with carmine solution and observed with the light microscope. All of the worms were identified with Concinnum ten (Yamaguti, 1939) Travassos, 1944 according to the measurement. The present paper is the first report showing that Concinnum ten was found from Meles meles and Mustela sibirica, and that these animals are also the natural final hosts of Concinnum ten.