Three patients with a DSM-III-R diagnosis of posttraumatic stress disorder were successfully treated with buspirone in final maximum dosages ranging from 35–60 mg daily. The onset of clinical efficacy ranged from 5–29 days. Symptoms that improved included anxiety, insomnia, flashbacks, and depressed mood. Patients experienced no side effects. Serotonin partial agonist effects are a possible mechanism underlying buspirone's efficacy.