Four workers were exposed to ethylene oxide gas. Acute encephalopathy occurred in one, and peripheral neuropathy in three, two of whom were symptomatic. Nerve conduction velocity studies were abnormal in three, including the asymptomatic patient. Decreasing the amount of exposure resulted in relief of symptoms. The abnormal nerve conduction studies did not change in two patients who continued to work at a lower level of exposure, whereas the conduction abnormalities improved in the patient who was removed from exposure.