Sleep patterns of two young female patients with congenital dopamine beta-hydroxylase deficiency are described. In this orthostatic syndrome central and peripheral noradrenergic failure occurs as a result of impaired beta-hydroxylation of dopamine. Consequently, the levels of dopamine and its metabolites are elevated. The relative importance of noradrenaline deficit in the face of dopamine excess for sleep-regulatory mechanisms can be inferred from the sleep pattern of these patients. No subjective sleep complaints were reported. The sleep patterns showed a high percentage of slow-wave sleep in both patients (29% and 34% of sleep period time) and a relatively low to normal percentage of REM sleep (18% and 21%). A normal cyclic REM sleep pattern was observed. Alpha-delta sleep occurred during light sleep (15% and 8%); consequently, the amount of stage 2 sleep was reduced. These results indicate that functional insufficiency of the noradrenergic system in two patients with dopamine beta-hydroxylase deficiency is not associated with profound changes in the (REM) sleep pattern. This supports a modulatory or permissive role for noradrenaline in REM sleep mechanisms.