Clinical improvement after coronary artery bypass surgery depends on the complete revascularization and patency of graft vessels. Patency rate and the factors influencing the patency were studied by examining 134 grafts in 55 patients at a mean follow-up of 22.8$pm$4.2 months, range 15 days and 108 months. Serial studies were performed on 7 patients with 18 grafts. The over-all patency rate was 80.6%, and the rate more than 5 years after surgery was 50.0% with mean interval of 81 months. Patency rate of patients who had taken both aspirin and dipyridamole was higher than of patients who had been treated with aspirin only[80.5% vs 56.5%]. The average serum triglyceride level of patients who had graft stenosis or occlusion in at least one site was significantly higher than that of patients in whom all grafts were patent[262.1mg% vs 174.8mg%]. Patency rate of grafts in patient who had angina was 73.2% and in patients without angina 79.2%. 6 patients underwent successful percutaneous transluminal angioplasty for narrowed or occluded grafts.