There are few effective treatments of antisocial personality disorder (APD). Preliminary work suggests that the atypical antipsychotic quetiapine can decrease irritability, impulsivity, and aggressiveness. Data were collected from 4 patients with APD who were referred to a maximum-security inpatient psychiatric facility for pretrial evaluation and were treated with quetiapine. Quetiapine was effective in these patients as was indicated by a decrease in symptoms such as impulsivity, hostility, aggressiveness, irritability, and rage reactions. Typical dosage was 600 to 800 mg per day. Patients attributed their willingness to comply with quetiapine treatment to both the effectiveness of the drug and its favorable adverse-event profile. Quetiapine was successfully combined with mood stabilizers, particularly gabapentin, in patients with prominent affective instability. Quetiapine has demonstrated efficacy in aggression, impulsivity, and irritability and has proved to be an effective medication in these patients with APD. In addition, its favorable adverse-event profile makes patients willing to comply.