Abstract: AIM: To study the impact of Captopril onvascular endothelium function in patients with essentialboundary hypertension. METHODS: We examined theendothelium-dependent vasodilation of brachial arteries in23 patients and 20 normal subjects by high -frequenceUltrasound. RESULTS: Though there were not significantlydifferences in vasodilation of brachial arteries during givenNitroglycerin between two groups (%:26.02 ±5.59 vs28.02 ±6.04, P >0.05), the change of dimater of brachialarteries during reactive hyperaemia decreased remarkablyin patients in contrast to the normal.Thechange became normal after patients having taken Captoprilfor three months (%:22.50 ±5.45 vs 6.34 ±2.43,P <0.05). CONCLUSION: There was some decreaseof vascular endothelium function in patients with essentialboundary hypertension.But the injured endothelium functioncould recover after given Captopril.

Key words: captopril, boundary hypertension, endothelium function, ultrasound