Positron emission tomography with 18F-deoxyglucose was used to evaluate regional brain glucose metabolism in eight normal subjects and eight psychiatric patients with a history of repetitive violent behavior. Seven of the patients showed widespread areas of low brain metabolism. Although the location of the abnormal regions varied among patients, they showed significantly lower relative metabolic values in medial temporal and prefrontal cortices than did normal comparison subjects. These regions have been implicated as substrates for aggression and impulsivity, and their dysfunction may have contributed to the patients' violent behavior.