Orthostatic hypotension in a patient with Shy-Drager syndrome was treated for 6 months with oral DL-threo-3,4-dihydroxyphenylserine (DL-threo-DOPS). Adrenergic function was evaluated before and during treatment by measurements of changes in blood pressure and plasma norepinephrine on head-up tilting and by the response of blood pressure to the Valsalva maneuver and infused norepinephrine. After the patient received DL-threo-DOPS, the fall in his mean arterial blood pressure on head-up tilting was reduced and he had no syncope when standing. When peripheral decarboxylase inhibitor was combined with DL-threo-DOPS, the same beneficial effect on orthostatic hypotension was observed.