The overall objective of our research is to delineate the effects of specific neurotoxicants on the neuroanatomy of the central nervous system. Our work has been centered around several topics including assessing the effects of exposure to organophosphorus compounds and polychlorinated biphenyls (PCBs) on the mature and developing avian and mammalian central nervous system, determining the effects of exposure to Great Lakes toxicants on the developing central nervous system, and studying the effects of administration of phenylmethylsulfonyl fluoride on the severity of organophosphorus-induced delayed neurotoxicity in developing chicks. Techniques employed include silver degeneration stains, immunocytochemistry, and quantitative imaging.