Impaired endothelial function has been reported to be the initial step in atherosclerosis. Some coronary risk factors independently relate to impaired endothelial function. However, few studies have examined the association between coronary risk factors and endothelial function in patients who have multiple risk factors without clinical atherosclerosis. This study was undertaken to elucidate the relationship between accumulation of coronary risk factors and vascular endothelial dysfunction. We examined 101 subjects with one or more coronary risk factors 56.8 +/- 1.0 years old and 40 age-matched control subjects without coronary risk factors. We measured brachial artery diameter non-invasively using a 7.5-MHz ultrasound machine at rest, during reactive hyperemia caused by endothelium-dependent vasodilatation, and after sublingual administration of nitroglycerin, which causes endothelium-independent vasodilatation. The percentage change in flow-mediated diameter (%FMD; deltaD/D x 100), in subjects with one or more coronary risk factors was significantly lower than that in control subjects(4.8 +/- 0.3% vs. 6.7 +/- 0.5%, p < 0.01). Endothelium-independent vasodilatation by nitroglycerin did not differ between the two groups. Endothelial function was impaired according to the accumulation of coronary risk factors. On multiple regression analysis, the number of risk factors, age, and brachial artery diameter at rest showed significant correlation with %FMD. Our results suggest that an accumulation of coronary risk factors was significantly related to impairment of endothelial function.