The decrease in renal blood flow (RBF) observed in patients with hypertension can be increased with converting enzyme inhibition (CEI). It is unknown whether the decrease in RBF observed with age can also be increased with CEI. This study compared the short‐ and long‐term effects of captopril monotherapy in young (65 years) hypertensive patients. Captopril effectively decreased blood pressure in both groups (diastolic blood pressure<90 mm Hg), with the young patients requiring a lower dose (.7 mg/kg) than the elderly patients (1.2 mg/kg). Creatinine and para‐aminohippurate clearances were maintained in both groups, with a decrease in renal vascular resistance being observed in the younger patients. Serum aldosterone levels fell significantly after each dose of captopril at all phases of the study, with no change observed in plasma renin levels. Atrial natriuretic peptide (ANP) level was increased in the elderly patients receiving placebo (48.8 ± 8 pg/mL) when compared with the young subjects (24 ± 3.8 pg/mL). Captopril did not alter ANP levels in eithe