A health survey of three groups of workers occupationally exposed to polychlorinated biphenyls (PCBs) was performed. Workers were employed in an electric equipment manufacturing facility and public and private utility companies. Ambient PCB concentrations and personal samples were assayed. Workers completed a questionnaire concerning work hygiene, alcohol and tobacco consumption, and family and personal medical histories. They were given physical examinations and standard complete blood and urine analyses, including cell counts, enzyme activity, and cholesterol determination. PCB components were quantitated as lower chlorinated biphenyls and higher chlorinated biphenyls using gas chromatography. Work environment PCB concentrations ranged from 0 to 264 micrograms per cubic meter (microg/m3), with the highest amount at the electrical equipment manufacturing facility. Skin smear samples showed PCB concentrations as high as 668microg/m3 (electrical equipment manufacturer) and 487microg/m3 (private utility). Mean serum low PCB concentrations among equipment manufacturing workers ranged from 8 to 50 times, and mean serum high PCB concentrations from 2 to 4 times the community background value. Mean serum low PCB values were much greater among workers at the equipment manufacturer than at the utilities, whereas high PCB values were comparable among these groups. Coughing, irritated eyes, loss of appetite, tingling in the hands, and rash or dermatitis were associated with both serum high and low PCB values. Serum PCB concentrations significantly correlated with glutamic-oxalacetic- transaminase, serum gamma-glutamyl-transpeptidase, and plasma triglyceride activity, and inversely correlated with plasma high density lipoprotein cholesterol. No overt clinical dysfunction was seen. The authors conclude that plasma chemical changes are evidence of the effect of PCB exposure on the liver and suggest that PCB exposure be minimized. Results with skin smear samples show that ambient air samples do not accurately register total PCB exposure.