An estimated 70-87% of patients who suffer from posttraumatic stress disorder (PTSD) experience sleep disruption. These patients have distressing dreams or nightmares in which the traumatic event is reexperienced, and they also have difficulty in falling or staying asleep. Selective serotonin reuptake inhibitors are the treatment of choice for PTSD, but with the exception of fluvoxamine, they are often ineffective or only partially effective for sleep problems. Sedative-hypnotics may be helpful in the short term but are associated with tolerance and addiction potential. In the central nervous system, alpha(1)-adrenergic receptors are known to be important in both the startle and sleep responses. Stimulation of these receptors may contribute to PTSD-related trauma-content nightmares. Prazosin, a highly lipophilic alpha(1)-adrenergic receptor blocker that is traditionally used to treat hypertension and benign prostatic hyperplasia, has been shown to decrease the occurrence of trauma nightmares in both combat veterans and patients with non-combat-related PTSD. The available data, although mostly from open-label trials, suggest that this agent also improves sleep quality and patients' sense of wellbeing and ability to function in daily activities. The optimum dose is unknown; however, a dose-related response appears to be evident. Clinicians should monitor for orthostatic hypotension, usually seen early in therapy, when prazosin is started in patients with PTSD.