PURPOSE: To diagnose the coronary artery disease, it is necessary to have a thorough knowledge on coronary anatomy and normal variations. We performed a morphological study on normal variations of coronary artery in Korean adults. MATERIALS AND METHODS: 1012 cases of coronary angiography were analyzed with particular emphasis on the normal variation of three coronary arteries and their major branches, including origin of conus artery, sinus node artery and atrioventricular node artery and the variation in posterior descending artery and ramus medianus. RESULTS: We found right dominance in 895 cases(88.4%), left domainance in 44 cases(4.3%), and balanced dominance in 73 cases(7.2%). Conus artery branched from right coronary artery in 468 cases(47.6%) and originated in right coronary sinus close to the os of right coronary artery in 515 cases(52.4%). Sinus node artery originated from left circumflex artery in 551 cases(54.4%), from right coronary artery in 442 cases(43.7%), and from both coronary arteries in 19 cases(1.9%). Atrioventricular node artery originated from right coronary artery in 943 cases(93.4%), from left circumflex artery in 59 cases(5.8%), and two atriovenricular node arteries from both arteries in 8 cases(0.8%). Posterior descending artery had the normal pattern in 505 cases(58.6%) and some variation in 357 cases(41.4%). We found short left main coronary artery, less than 2--3 mm, making it hard to cannulate in 172 cases(17.0%). Ramus medianus was found in 165 cases(16.5%) with marginal distribution in 84 cases(8.4%), diagonal distribution in 80 cases(8.0%) and coursing interventricular sulcus as double left anterior descending artery in 1 case(0.1%). Left main coronary artery gave off 4 branches in 8 cases(0.8%). Myocardial bridging was found in only 3 cases(0.3%). CONCLUSION: This study could provide basic morphological data on anatomy and normal variations of coronary arteries in Korean adults.