BACKGROUND AND OBJECTIVES: Hyperhomocyt(e)inemia is known to be one of independent risk factors for atherosclerosis. The relationship between hyperhomocysteinemia and coronary artery diseases was evaluated in Korean adults. MATERIALS AND METHOD: Basal fasting plasma homocysteine level was measured in 307 patients (174 males, 58+/-11 years; 133 females, 60+/-11 years). Coronary artery disease (CAD) was diagnosed in 194 patients. According to the clinical presentation of CAD and the number of significantly stenotic coronary artery, the plasma homocysteine level was analyzed. RESULTS: The plasma homocysteine level was 9.4+/-3.0 micromol/L in male and 8.5+/-3.5 micromol/L in female (P=.016). Homocysteine was 10.0+/-3.3 micromol/L in 130 smokers, 8.3+/-3.0 micromol/L in 162 non-smokers (P<0.001). The plasma homocysteine level was 9.4+/-3.2 micromol/L in 194 patients with CAD and 8.4+/-3.2 micromol/L in 113 patients without CAD (P=.008). The homocysteine was 10.2+/-3.2 micromol/L in 63 patients with acute myocardial infarction (MI), 9.8+/-3.1 micromol/L in 37 old MI, 8.7+/-3.0 micromol/L in 67 unstable angina, and 8.8+/-3.7 micromol/L in 27 stable angina. The plasma homocysteine was related with the clinical presentation of CAD(P=.035) but was not an independent risk factor for coronary artery diseases. CONCLUSIONS: The elevated value of plasma homocysteine level is a risk factor for pateint with clinical severity of the coronary artery diseases, and male and smokers had higher plasma homocysteine level than those in female and nonsmokers.