BACKGROUND: Coronary artery ectasia is an abnormal enlargement of coronary artery and infrequently associated with acute coronary syndrome. The prognosis, treatment, and etiology of this disease remain unclear. METHOD: Sixty-one patients (35 male and 26 female, 53+/-11.0 years) out of 4,694 patients who underwent diagnostic coronary angiography at Chonnam National University Hospital between January 1996 and March 1999, and diagnosed as isolated coronary artery dilatatation without significant stenosis, were analyzed retrospectively. RESULTS: The incidence of coronary artery ectasia on the coronary angiography was 1.29%. Smoking was the most frequently associated risk factor. Clinical diagnosis was 16(26.2%) cases of stable angina, 29(47.5%) unstable angina, 9(14.7%) acute myocardial infarction, 5 (8.1%) old myocardial infarction, and 2(3.3%) variant angina. Right coronary artery was the most frequent involved artery (42.5%). Type I according to Markins' classification was 63.9%. Proximal part of coronary artery was the most common involved arterial segment. Aspirin (78.7%), calcium antagonist (73.8%), nitrate (29.5%) and beta-blocker (12%) were used. During clinical follow-up of 12+/-10.5 months, there were no major cardiac event in all patients. CONCLUSION: The incidence of the coronary artery ectasia in Korean patients was relatively rare, and long-term prognosis was good.