Long-term effects of bilateral prefrontal lesions were studied in 14 lobotomized schizophrenic patients who were operated in the fifties. CT scans revealed cystic bilateral frontal lesions in almost every patient and cortical atrophy was seen in 5 patients. The prefrontal syndrome was severe in 1 patient, marked in 1 patient, mild in 9 patients and absent in 3 patients. Primitive reflexes could be elicited in 2 patients, 3 patients suffered from epileptic seizures, and 8 from minor motor defects. Four patients committed a homicide in the period after the operation, which indicates that the frequency of committing homicidal acts had doubled when compared with the situation before the operation. The incidence of homicides after lobotomy is extremely high considering that all patients except 1 were kept under continuous observation in hospitals.