To examine whether moderate hyperhomocyst(e)inemia is associated with coronary artery disease and the number of diseased coronary vessels in Koreans, we investigated 201 patients with angiographically documented coronary artery disease and 187 healthy subjects without evidence of stroke and coronary artery disease. The mean plasma total homocysteine in patients was higher than in controls (10.3 micromol/L; 95% confidence interval, 7.0-13.6 vs. 8.9 micromol/L; 6.0-11.8) (p=0.005). The prevalence of moderate hyperhomocyst(e)inemia, defined as the top 90th percentile in controls (13.2 micromol/L), was higher in patients than in controls (23.9% vs. 10.2%, p=0.001). Plasma homocyst(e)ine levels were not correlated to age, body mass index, levels of serum cholesterol, creatinine, and uric acid. Based on multiple logistic regression analyses with adjustment for total cholesterol, hypertension, smoking status, diabetes, age, and body mass index, the adjusted odds ratio of moderate hyperhomocyst(e)inemia for coronary artery disease was 1.53 (95% confidence interval: 1.39-1.65, p=0.0001). Moderate hyperhomocyst(e)inemia, diabetes mellitus, and old age were more prevalent in patients with triple-vessel disease than in single- or double-vessel disease (p=0.02). Multiple logistic regression analysis revealed that moderate hyperhomocyst(e)inemia was a significant predictor of triple-vessel disease with odds ratio of 2.78 (95% confidence interval: 1.08-7.10, p=0.02). We conclude that moderate hyperhomocyst(e)inemia is an independent risk factor for coronary artery disease, and also related significantly to the presence of triple-vessel disease.