BACKGROUND AND OBJECTIVES: Although the size of the coronary artery is known to be closely related to the outcome of coronary artery bypass grafting and percutaneous coronary intervention, its normal value and determinants have not been examined in Koreans. SUBJECTS AND METHODS: One hundred and twenty seven normal coronary arteriograms were carefully selected from 3,412 studied consecutively. Of these, 53 women and 23 men, with no abnormalities in their cardiac function and not using nitrates, were studied. The lumen diameter was measured at 10 segments in the epicardial coronary arteries. RESULTS: For men, the mean lumen diameter of the proximal left anterior descending and left circumflex coronary arteries were 3.88+/-0.39 and 3.45+/-0.47 mm, respectively, and were not affected by the anatomic dominance. However, the left main and proximal right coronary arteries varied between 4.44+/-0.49 and 5.18+/-0.32 mm (p<0.05) and 3.29+/-0.60 and 4.05+/-0.42 mm (p<0.05), respectively, by the anatomic dominance. Women had a smaller mean coronary artery size than men [for diameter, -7% (p<0.01);for cross-sectional area, -13% (p<0.01)], and the left ventricular (LV) mass was significantly associated with coronary artery diameter (p<0.05). From a multiple linear regression analysis, gender was an only independent predictor of the coronary artery size (p<0.05). CONCLUSION: We revealed normal coronary artery dimensions in Koreans. Although, body size, hypertension, use of calcium channel blockers, anatomic dominance and age had no effect on the size of the coronary artery, but the LV mass and gender were shown to have an effect. The multivariate regression analysis showed gender was an only independent predictor of the coronary artery size.