BACKGROUND AND OBJECTIVES: Homocysteine is a metabolite of methionine metabolism with atherogenic and thrombotic properties. Increased blood homocysteine has been recognized as a risk factor for atherosclerotic coronary artery disease, but it is not much to be clarified in this country. MATERIALS AND METHOD: In a case-control study, we examine the relationship between the risk of atherosclerotic coronary artery disease and serum total homocysteine, folate, vitamin B12, vitamin B6, and other conventional risk factors. Thirty nine patients with significant stenosis of epicardial coronary artery and 20 healthy age-sex matched control subjects were included. Fasting venous blood was obtained and serum total homocysteine (tHCY) concentration was measured by high performance liquid chromatography and fluorescent detection method. RESULTS: Compared with control group, case group had higher tHCY concentrations (14.9+/-6.9 vs 10.8+/-4.2 mol/L, p<0.05) and lower folic acid concentration (6.7+/-3.6 vs 11.0+/-5.7 ng/mL,p<0.05). There were higher tHCY concentrations of patients with 2 vessel and 3 vessel disease than that of patients with 1 vessel disease (17.2+/-6.7 and 18.4+/-9.8 micro mol/L vs 12.4+/-3.9 micro mol/L,p<0.05). Vitamin B12 and vitamin B6 concentrations showed no significant difference between case group and control group. Compared with control group, there were more smokers (51.5% vs 25.0%, p<0.05), and patients with hypertension (39.4% vs 0%, p<0.001) and diabetes (30.3% vs 0%, p<0.001) in case group. Increased tHCY (tHCY over 14.7 mol/L) was an independent risk factor for atherosclerotic coronary artery disease (OR; 6.75, 95% CI; 1.15 - 40.99, p<0.05) together with smoking (OR; 5.4, 95% CI; 1.22 - 23.95, p<0.05). CONCLUSION: These data support the hypothesis that elevated serum tHCY concentration is a risk factor for Korean patients with atherosclerotic coronary artery disease, and low folate concentration may be responsible for elevated tHCY concentration.