Objective To investigate the relationship between vascular endothelial dysfunction and serum homocysteine (HCY)level in patients with coronary lesions.Methods Serum HCY, serum nitric oxide (NO), plasma endothelin-1 (ET-l), and circulation endothelial cell (CEC) were measured in 76 patients who received coronary angiography. Fifty-four patients with a stenosis of 50% or more at least in one coronary atery were as coronary artery disease (CAD) group. Other 22 cases with no recognizable plaque and/or stenosis were as control group. HCY level was detected using an enzyme immunoassay kit. NO concentration was measured using a nitrate reductase kit. Radio-immunoassay was applied to analyse the ET-1 level, and CEC was measured by flow cytometry.Results The levels of HCY, ET-l, and CEC in patients with coronary lesions were significantly increased in comparison with control group (P ＜ 0.01), while NO level in CAD group was significantly lower compared with that in control (P ＜0.01). Using a multivariate stepwise regression analysis, HCY level had a positive correlation with ET-1 level (r = 0.420, P ＜0.05) and CECs number (r = 0.423, P ＜ 0.05); and had a negative correlation with NO/ET-1 (r = -0.403, P ＜ 0.05). But there was no significant correlation between HCY and NO levels.C, onclusions HCY might lead to endothelial cell injury, which would provide a plausible mechanism for the relationship between hyperhomocysteinemia and development of coronary artery disease. HCY can be considered as a predictor for preliminary or active coronary lesion.