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.