Plerocercoid larvae of Proteocephalus ambloplitis are common among native basses in a south-western West Virginia (U.S.A.) reservoir managed by the West Virginia Department of Natural Resources. Liver pathology induced by these larval cestodes in small black basses (i.e. length < 305 mm for largemouth bass Micropterus salmoides; < 254 mm for spotted bass, M . punctulatus) is characterized by extensive areas of pressure necrosis with macrophage infiltration adjacent to the parasite tegument, but with little evidence of blood vessel congestion or fibrosis. Parasitized livers of larger bass (i.e. 2 305 mm for largemouth, 2254 mm for spotted) showed considerable damage with blood vessel congestion, bile-stasis and extensive fibrosis, along with degenerating as well as migrating plerocercoids. The prognosis for survival of the smaller hosts, with 16.7 and 8.7 larvae per liver for largemouth and spotted bass, respectively, is questionable.