The EEG of five patients poisoned by an agricultural organofluoride (Nissol) were studied. The mild cases showed almost no abnormalities, but as the intoxication became severe, the EEG ragned from low-voltage, irregular slow waves to almost flat waves. However, a good response was observed to glucose administration even in these cases. The close association of an impaired carbohydrate metabolism as manifested by hypoglycemia in organofluoride poisoning would be an important point in the differential diagnosis from other types of pesticide poisoning and EEG appears to be a useful procedure for the evaluation of intoxication.