Several capacitors containing polychlorinated biphenyls (PCB) exploded in a cardboard plant. During the accident, and in the clearing work, several workers were in probable contact with PCB and/or its degradation products. Nausea, intense perspiration, and headache were acute symptoms, which cleared quickly. The 15 men with the greatest exposure were studied neurophysiologically twice, namely, two and six months after the explosion. Motor conduction velocities (MCV) of the right median, ulnar, and peroneal nerves; sensory conduction velocity (SCV) of the right sural nerve; and distal SCVs of the right median and ulnar nerves were measured with skin electrodes. Thirty male workers with a similar age distribution served as referents. Two months after the explosion all SCVs and distal SCVs were slower in the exposed men, and still six months after the explosion the distal SCV of the ulnar nerve and the SCV of the sural nerve were slightly slower among the exposed. However, clear improvement occurred in the distal SCVs during the follow-up. As in many toxic distal axonopathies, the distal SCVs were reversibly impaired after an accidental exposure to PCB fumes. PCB seem to exhibit neurotoxic properties in humans.