It reviews genetic studies involving sex-chromosomal abnormalities, family and twin studies, and adoption studies. It looks at sex differences in aggression and autonomic nervous system (skin conductance) studies involving testing of emotionality and emotional responsiveness, spontaneous responses and responses to stimulation, skin conductance recovery, and skin conductance and violence. Neurophysiological studies, based on electroencephalographic evaluation of central nervous system functioning, are reviewed, and neuropsychological evidence allowing inferences relevant to localization and lateralization of brain dysfunction is explored. Classification schemes of violent offenders based on neurophysiological and neuropsychological findings are presented, and pharmacological and biochemical factors that may be related to violence are examined. Among the exogenous substances discussed are alcohol, amphetamines, phencyclidine, marijuana, and opiates. The endogenous substances include testosterone and glucose. The aspects of central and autonomic nervous system functioning discussed are, in part, genetically determined. The literature strongly suggests that many violent offenders suffer organic brain dysfunction. The evidence, however, does not imply that the origins of this dysfunction are genetic; rather, it is likely that organic impairments result from environmental events that include cerebral trauma. The utility of aberrant biological features as predictors of antisocial behavior among persons who experience criminogenic social conditions is limited; however, biological features may be useful in understanding the resistance to commit criminal behavior. A graph, 2 tables, and about 300 references are included.