A 5-year-old girl with an apparently normal premorbid personality and adjustment became acutely psychotic following a single accidental ingestion of 100μg of d-lysergic acid diethylamide (LSD), with agitation, panic, depression and flattening of affect, disorientation, feelings of depersonalization, distortion of body image, and depression of intellectual functioning. In addition she displayed evidences of organic brain dysfunction: impaired visual-motor and visual-perceptual functions, and abnormality of the electroencephalogram. Within days the most florid evidences of disturbance had disappeared but the thinking disorder, distortion of body image, and depression of intelligence quotient persisted for several months. At the end of five months the only residua were the abnormal EEG and disorganization of visual-motor functions. At the end of nine months only the visualmotor functions remained impaired.