In hypertensive patients with a history of stroke, inappropriate antihypertensive therapy can reduce cerebral blood flow (CBF), exposing patients to the danger of cerebral ischemia, An angiotensin-converting enzyme (ACE) inhibitor, alacepril (25 mg twice daily after meals in the morning and evening), was orally administered for 4 weeks to 12 hypertensive stroke patients, and CBF was measured using 133Xe inhalation methods before and after alacepril treatment. After 4 weeks of treatment, systolic and diastole blood pressures decreased by 18 +/- 12 mm Hg and 9 +/- 5 mm Hg, respectively, The CBF increased significantly by 10.6 +/- 16.5% (P < 0.05) in the diseased cerebral hemisphere and by 12.5 +/- 14.8% (P < 0.01) in the healthy cerebral hemisphere, None of the patients had symptoms of cerebral ischemia during the treatment period, Chronic ACE inhibition is known to ameliorate the mechanics and function of cerebral arteries and improve quality of life, including cognitive function, The increase in CBF seen in our patients may reflect the reduction of cerebrovascular resistance and improvement of cerebral function, Our results suggest the potential usefulness of ACE inhibitors in antihypertensive therapy for stroke patients.