Nitroglycerine-induced vasodilation (NID) is usually measured as a control test for flow-mediated vasodilation (FMD). However, NID per se is also associated with atherosclerosis. The purpose of this study was to determine the relationships among NID, FMD and blood pressure, and to evaluate the effects of antihypertensive therapy on NID in patients with hypertension. We measured NID and FMD simultaneously in 94 subjects, including 35 normotensive subjects, 26 patients with stage 1 hypertension (⩾140/90 mm Hg) and 33 patients with stage 2 hypertension (⩾160/100 mm Hg), and we evaluated the effect of antihypertensive therapy for 4 weeks on vascular function in 14 patients with hypertension. NID was smaller in patients with stage 2 hypertension than in patients with stage 1 hypertension and normotensive subjects (10.5±3.9% vs. 13.8±5.0% and 16.2±5.7%; P<0.05, respectively), whereas there was no significant difference in NID between normotensive subjects and patients with stage 1 hypertension. FMD was smaller in patients with stage 2 and stage 1 hypertension than in normotensive subjects (3.1±2.7% and 4.1±1.5% vs. 6.4±2.7%; P<0.05, respectively), whereas there was no significant difference in FMD between patients with stage 1 hypertension and those with stage 2 hypertension. After 4 weeks of antihypertensive therapy, NID was enhanced from 11.9±3.4% to 14.0±3.7% (P=0.03) in patients with hypertension. There was a significant relationship between the decrease in diastolic blood pressure and the increase in NID (r=-0.35, P=0.04). Both NID and FMD were impaired in patients with stage 2 hypertension. Four-week antihypertensive therapy improved NID in patients with hypertension.