Fertile white leghorn chicken eggs were exposed to 0, 1, 2, 4, 6, 8 or 16 microliters of Prudhoe Bay Crude oil (PBCO) on day 9 of incubation. The effects of oil on pipping and hatching success, body weight gain after hatching, serum creatine kinase levels, and pathological changes in organ systems were assessed in embryos that had survived acute toxic effects and were alive on day 18 of incubation. Exposure to oil greatly reduced pipping and hatching success. Severe edema and hemorrhage in the pipping muscle, multifocal subcapsular hepatic necrosis, marked depletion of lymphocytes in the bursa of Fabricius with infiltration by heterophils, and occasional dorso-caudal subcutaneous edema were observed in treated embryos. Pipping muscles were heavier in oil-exposed embryos. Embryos exposed to 4 microliters of PBCO had significantly reduced gain in body weight post-hatching. Serum creatine kinase levels were significantly elevated in the oil-exposed embryos only at the time of hatching. There was no evidence that exposure to oil caused degenerative changes in pipping muscle cells.