The status of polychlorinated biphenyls (PCBs) was discussed in regard to their manufacture and industrial applications; disposal; presence in the environment; accumulation in the food chain, including their toxicity, metabolism, and embryotoxicity in nonhuman species; acute exposure in humans; occupational and chronic exposure in humans; and issues for the present and the future. An estimated 270 million kilograms of PCBs was estimated to have been buried in North American landfill dumps up until 1972. Traces of PCBs were demonstrated in virtually every living species and in every stretch of land and water examined. In general, adverse effects on mammalian reproduction tended not to be manifested until the food content, dosage, or tissue level of PCBs reached 10 parts per million or more. The two most serious outbreaks of acute human PCB poisoning occurred in Japan in 1968, with 22 deaths from ingestion of contaminated rice-oil, and in Taiwan in 1979, with 24 deaths from ingestion of contaminated rice-bran-oil. Clinical responses to occupational PCB exposure included chloracne, rashes, nail pigmentation and deformity, ocular burning and edema, pigmentation of the conjunctiva, immunological abnormalities, nausea, lassitude, anorexia, digestive disturbances, impotence, sensory neuropathy, hematuria, and hepatic involvement. The author concludes that effective PCB disposal facilities are vital if the destruction of existing stocks is to be achieved safely, and that continuing vigilance will remain a valuable guard against accidents in the form of unforeseen random exposure both to PCBs and to their toxic degradation products.