A 66-year-old man with progressive supranuclear palsy is described. Although generally apathetic, withdrawn, and spontaneous in speech and behavior, he had sudden episodes of agitation, during which he was verbally threatening and physically abusive. Treatment with thiothixine and then with carbamazepine was ineffective in controlling his violent behavior. He responded temporarily to trazodone, and a recurrence of aggressive behavior was suppressed by increasing the dose of trazodone; this response may be related to trazodone's putative effect on the serotonin system. Although both carbamazepine and trazodone have been advocated for the control of aggression in organically impaired patients, they were not equally effective in this case.