Advances in our knowledge of the neurobiology of aggression and violence has given rise to rational pharmacological treatments for these behaviors. The main biological systems which are known to be involved are the neurotransmitters serotonin, norepinephrine, and gamma-aminobutyric acid (GABA), and electrophysiological activity in the brain. Abnormal functioning of these systems may also be complicated or caused by abuse of various psychoactive substances, particularly alcohol and stimulants. Adding further to this interaction is the high incidence of psychiatric disorders in the substance-using population, providing other behavioral influences and accompanying neurobiological dysregulation. Understanding of the interaction of these components has led to success in the treatment of aggressive and violent behaviors using selective serotonin reuptake inhibitors (SSRI's), lithium carbonate, beta-adrenergic blockers, anticonvulsants, anxiolytics, neuroleptics, and novel agents such as anti-androgens and serenics.