The frequency of atherosclerotic lesions of the abdominal aorta has reportedly increased significantly in chickens exposed to benzo[a]pyrene and 7,12-dimethylbenz[a,h]anthracene. The present studies were performed to determine in another experimental model frequently used in atherosclerotic studies, i.e., white carneau pigeons, whether these and other chemical carcinogens enhanced atherosclerosis. The induction and enhancement of atherosclerotic lesions were observed in pigeons treated with 7,12-dimethylbenz[a,h]anthracene, benzo[a]pyrene and 3-methylcholanthrene. The number and size of plaques in the aorta were frequently greater in pigeons treated with the higher concentration, i.e., 100 mg/kg of these 3 polycyclic aromatic hydrocarbons [PAH]. Benzo[e]pyrene and 2,4,6-trichlorophenol were ineffective in the induction or enhancement of atherosclerosis in the pigeons. The PAH (excluding benzo[e]pyrene) may have the only potential atherogens in avian atherosclerosis. This relationship may have been associated with how these hydrocarbons were transported in the plasma, i.e., by lipoproteins.