Dipetalonema spirocauda were found in 17 of 369 (4.6%) free-living ringed seals (Phoca hispida), 4 of 47 (8.5%) spotted seals (Phoca vitulina largha), 17 of 99 (17.2%) harbor seals (Phoca vitulina richardii), 1 of 19 (5.3%) ribbon seals (Phoca fasciata), and 2 of 51 (3.9%) bearded seals (Erignathus barbatus) collected from March, 1975 through September, 1979 in Alaskan waters. This is the first report of D. spirocauda in ribbon and bearded seals. Certain species of marine mammals from the families Ursidae, Otarridae, Odobenidae, Balaenidae, Phocaenidae and Monodontidae also were examined but none was found to be infected.