A-50-year-old woman was admitted to our hospital for the examination of exertional chest pain. She had no coronary risk factors. No hormonal disorders were observed. Physical and laboratory examinations revealed that she had not suffered from syphilis or aortitis syndrome or any other inflammatory diseases. An exercise electrocardiogram (Master's test) demonstrated ST segment depression in V3-6, II, III and a VF. On coronary angiography, a 75% stenosis of the left coronary ostial stenosis was found, but no abnormality was found in other arterial trees. The patient was diagnosed as having isolated coronary ostial stenosis. She underwent coronary bypass surgery from the aorta to the circumflex artery and the anterior descending coronary artery. She is now completely asymptomatic. A review of the literature together with this patient reveals the following characteristics of patients with isolated coronary ostial stenosis. Firstly, the patients are almost always middle aged woman with no coronary risk factors. Secondly, the involved coronary artery is the left main coronary artery, so its obstruction results in a serious condition. Therefore, though its pathogenesis remains to be determined, isolated left coronary ostial stenosis seems to be a distinct clinical entity.