Prominent heightened arousal symptoms and clinical/laboratory findings implicate the central noradrenergic system in posttraumatic stress disorder (PTSD). Heightened arousal frequently manifests in relation to sleep in PTSD. Central noradrenergic systems have a role in regulating arousal levels during sleep. We therefore evaluated noradrenergic production via urinary excretion in relation to sleep/wake activity in PTSD patients and controls. Twenty patients--all Vietnam veterans diagnosed with combat-related PTSD--and eight non-ill, non-combat-exposed controls had overnight sleep studies under medication and substance-free conditions. In association with sleep recording, subjects saved their urine for 24 hours in three 8-hour collections in order to obtain "daytime" (8:00 AM to 4:00 PM, 4:00 PM to MN) and "nocturnal" (MN to 8:00 AM) catecholamine measures. PTSD patients had decreased sleep efficiency relative to controls and increased REM density; 24-hour norepinephrine and MHPG (the more centrally derived metabolite) did not differ between patients and controls. "Nocturnal" excretion of MHPG minus the average of the two "daytime" values was negative in the controls, slightly positive in the patients, and differed significantly between the two groups. "Nocturnal minus daytime" MHPG also correlated negatively with total sleep time in the PTSD patients (R = -.45, p < .05). Our data support a relationship of nondiminished central noradrenergic activity at night, and sleep disturbance, in chronic, combat-related PTSD.