AbstractNeuropsychological functioning, diagnoses, and substance abuse were compared among killers, nonhomicidal assaulters, and nonviolent offender controls. The Reitan and Luria‐Nebraska Neuropsychological test batteries, the WAIS‐R, CT scans, and EEGs were examined with a trend to more neuropathology found in killers and assaulters than in controls. There were no group differences in ICD‐9 diagnosis nor on the MMPI, although considerable personality pathology was noted in all groups. Violent offenders scored higher on the Michigan Alcoholism Screening Test (MAST). The violent offenders were more likely to experience alcohol and drug‐related mood dysphoria. The interaction of neuropsychological, personality, and substance abuse variables is di