Aroclor 1242, a chlorinated biphenyl, is widely used as a dielectric medium in transformers and capacitors. In this survey, thirty-four occupationally exposed workers were examined. Complaints consisted of a burning sensation of the face and hands, nausea, and a persistent body odor. One had chloracne, and five suffered from an eczematous rash on the legs and hands. Although hepatic function tests were normal, the mean blood Aroclor level in the exposed group (approximately 400 ppb) was significantly higher than in the control group. A tentative value of 200 ppb is suggested for Aroclor 1242 as an acceptable level for occupationally exposed workers. The use of an efficient exhaust ventilation to maintain air concentrations below the threshold limit value, and the regular measurements of hepatic function and of blood Aroclor concentrations in exposed workers are recommended.