BackgroundA number of reports have indicated that carbamazepine (CBZ) may be effective in the treatment of aggressive behavior. It has been suggested that performance on the Wisconsin Card Sorting Test (WCST) may be a marker for this antiaggressive effect. We report on a multiple crossover trial of CBZ monotherapy of a violent forensic patient.MethodA man with organic personality syndrome and a history of violent behavior received CBZ monotherapy in an A-B-A-B design with measures of behavior, mood, and WCST scores collected during each phase of the study.ResultsThe patient exhibited significant decreases in hostility, improvement in mood, and increased WCST performance in response to CBZ therapy. This improvement was reversed when CBZ was withdrawn and was restored when CBZ was subsequently reintroduced.ConclusionThis pattern provides support for the literature documenting the antiaggressive effect of CBZ. It supports the suggestion that the WCST may be a marker for that effect, and that the frontal lobe may be the site of its mechanism of action.