The author describes a case of acute poisoning by endosulfan (a chlorinated hydrocarbon insecticide) in an industrial worker, with residual psychiatric syndrome. The acute phase was manifested by repeated convulsions and impaired consciousness. After recovery the patient became disoriented and agitated. The residual phase, 2 years after initial hospitalization, was manifested by cognitive and emotional deterioration, severe impairment of memory and inability to perform any but the simplest tasks. Psychological tests revealed gross impairment of visual-motor coordination. The differential diagnosis of chronic brain syndrome requires accurate history and milder cases of endosulfan poisoning may easily be overlooked or misdiagnosed.