Nine patients with mild or moderate essential hypertension were studied at the Vargas Hospital of Caracas, Venezuela. After antihypertensive treatment discontinuation, all patients were placed on placebo during a 1-week period, after which domperidone, a peripheral DA(2) dopaminergic blocker, was orally administered at the dose of 20 mg every 12 h during a period of 1 week. A final 1-week period of bromocriptine, 2.5 mg orally every 8 h, followed the domperidone period. Cold pressor test caused an increase of mean blood pressure and of heart rate, which was more accentuated after adding bromocriptine. Domperidone also caused an increase of serum aldosterone levels. Our results suggest that a dopaminergic mechanism is acting during the cold pressor test and during aldosterone secretion.