BACKGROUND: Isolated coronary ostial stenosis presumed to be atherosclerosis in origin is a rare condition reported to have peculiar characteristics-that occurs primarily in premenopausal women, low incidence of risk factors, severe symptoms of short duration with absence of collaterals suggesting rapid development. METHODS: From Feb. 1979 to May. 1991, 11 patients with isolated left coronary ostial stenosis were identified among 2520 coronary angiographies and they were presumed to be athreosclerosis in origin by excluding other alleged causes. RESULTS: There were 5 males and 6 females with mean ages of 47.8+/-9.5 and 51.5+/-7.9 respectively. Clinical presentations were stable angina in 4, unstable angina in 6 patients, and unstable angina after myocardial infarction in 1 patient.Number of risk factors per patient was 0.82+/-0.98. Majority showed a relatively short history of angina(mean 3.6+/-2.8 months). Coronary angiographic findings showed collateral circulation in 7 patients-grade III in 5 of them. There was 1 death related to coronary angiography. Coronary artery bypass surgeries were performed in 7 patients and 5 of them were followed for mean 22+/-8 months without coronary events. CONCLUSIONS: In contrast to the previous reports, isolated left coronary ostial stenosis presumed to be atherosclerosis in orign did not showed female predelication and although their symptom durations were relatively short coronary angiographies showed well developed collaterals in the majority of patients.We experienced one coronary angiography related death in this group of patients. Coronary artery bypass surgery is to be recommended in these patients otherwise contraindicated.