Objective: The presence of endothelial dysfunction in the coronary circulation or in the brachial artery has been found to be associated with a greater incidence of cardiovascular events. However, no data are presently available about the prognostic role of endothelial dysfunction in human small resistance arteries. Design and methods: Ninety subjects were included in the present study. They were: 10 normotensive subjects, 36 patients with essential hypertension, 10 patients with phaeochromocytoma, 11 patients with primary aldosteronism, 10 patients with renovascular hypertension, and 13 normotensive patients with non-insulin-dependent diabetes mellitus(NIDDM). All subjects were submitted to a biopsy of subcutaneous fat from the gluteal or the anterior abdominal region. Small resistance arteries were dissected and mounted on an isometric myograph, and the concentration-response curves to acetylcholine(from 10-9 to 10-5 mol/l)(endothelium-dependent vasodilatation) and sodium nitroprusside(from 10-9 to 10-5 mol/l)(endothelium-independent vasodilatation) after precontraction of the vessels with norepinephrine were evaluated. The subjects were re-evaluated(by clinical visits or telephone interviews) after an average follow-up time of 5.5 years. Results: Twenty-nine subjects had a documented fatal or non-fatal cardiovascular event(5.87%/year). The endothelium-dependent vasodilatation in the subcutaneous small arteries was similar in subjects with or without cardiovascular events. Also, endothelium-independent vasodilatation to sodium nitroprusside was similar in the two groups. Similar results were obtained by subdividing patients in the different subgroups(essential hypertension, secondary hypertension, etc.). Conclusions: Our results indicate that endothelial dysfunction in the microcirculation does not predict cardiovascular events. It is possible that a prognostic role of endothelial dysfunction may be observed when other vascular districts prone to atherosclerosis are evaluated, or it might be detected only in patients at low to medium cardiovascular risk, in whom endothelial dysfunction is less advanced. Objective: The presence of endothelial dysfunction in the coronary circulation or in the brachial artery has been found to be associated with a greater incidence of cardiovascular events. However, no data are presently available about the prognostic role of endothelial dysfunction in human small resistance arteries. Nine patients were included in the present study. They were: 10 normotensive subjects, 36 patients with essential hypertension, 10 patients with phaeochromocytoma, 11 patients with primary aldosteronism, 10 patients with renovascular hypertension, and 13 normotensive patients with non- insulin-dependent diabetes mellitus (NIDDM). All subjects were submitted to a biopsy of subcutaneous fat from the gluteal or the anterior abdominal region. Small resistance arteries were dissected and mounted on an isometric myograph, and the concentration-response curves to acetylcholine (from 10-9 to 10-5 mol / l) (endothelium-dependent vasodilatation) and sodium nitroprussi After (from 10-9 to 10-5 mol / l) (endothelium-independent vasodilatation) after precontraction of the vessels with norepinephrine were evaluated. The subjects were re-evaluated (by clinical visits or telephone interviews) after an average follow-up Time of 5.5 years. Results: Twenty-nine subjects had a documented fatal or non-fatal cardiovascular event (5.87% / year). The endothelium-dependent vasodilatation in the subcutaneous small arteries was similar in subjects with or without cardiovascular events. Also, endothelium-independent vasodilatation to sodium nitroprusside was similar in the two groups. Conclusions: Our results indicate that endothelial dysfunction in the microcirculation does not predict cardiovascular events. It is possible that a prognostic role of endothelial dysfunction may be observed when other vascular areas prone to atherosclerosis are evaluated, or it might be detected only in patients at low to medium cardiovascular risk, in whom endothelial dysfunction is less advanced.