BACKGROUND: A stenosis of left main coronary artery has critical prognostic importance. Recent reports on successful left main stenting are now challenging traditional treatment patterns for this lesion. We evaluated recent four-year trends in incidence, clinical, angiographic findings and treatment modalities in patients with left main coronary artery stenosis(LMS). METHODS: Patients who were diagnosed as a significant LMS at Yonsei cardiovascular hospital between 1996 and 1999 were analyzed retrospectively. RESULTS: The incidence of LMS during the period of 1996 to 1999 was 3.3%(n=24) and it was significantly higher than that of previous 15 years before 1996(p<0.01). The incidence of isolated ostial lesion was 0.28% and this lesion was more prevalent in young female patients with less risk factors compared with other types of LMS(p<0.01). After exclusion of the patients with an isolated ostial lesion, patients were grouped according to the lesion site: ostium, shaft, and shaft lesion extended to distal vessels. There were no differences in clinical and hemodynamic findings among these groups. Coronary artery bypass graft was performed in 141 patients(63%) and stent implantation in 16 patients(14%). CONCLUSION: The incidence of LMS has been increased. There was no difference in clinical and hemodynamic findings according to the types of LMS. Surgery is still a standard treatment, but in selected patients percutaneous coronary intervention can be another treatment option.