We studied the effects of bromocriptine therapy (mean dosage, 56.0 mg daily) for 12 months in five patients with both Parkinson's disease and hypertension. Therapy improved neurologic manifestations and reduced both supine and standing systolic blood pressures and standing diastolic blood pressure with no consistent change in heart rate. Transient episodes of orthostatic hypotension appeared in two cases. Domperidone (60 mg daily for 1 month) did not abolish the antihypertensive effect of bromocriptine, suggesting that central dopaminergic or alpha-adrenolytic mechanisms are involved in this effect. Bromocriptine may be useful in the treatment of hypertension in patients with Parkinson's disease.