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-1), 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-1, 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. Conclusions 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 preli-minary or active coronary lesion. 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- 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. Radio-immunoassay was applied to analyze the ET-1 level, and CEC was measured by flow cytometry. Results The levels of HCY , ET-1, 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 than with that in control (P <0.01). 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, (r = -0.403, P <0.05). But there was no significant correlation between HCY and NO levels. Conclusions 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 preli-minary or active coronary lesion.