BACKGROUND: Previous studies indicated that there was important correlation between early patency of infarct-related artery, preservation of ventricular function, and improved survival after thrombolytic therapy for acute myocardial infarction. An increased infusion rate of rt-PA has been shown to result in faster thrombolysis and a high patency rate of occluded vessel in myocardial infarction. Therefore, we evaluated the effect of simplified triple bolus injection of rt-PA on early patency of infarct-related artery and evaluated safety and efficacy of triple bolus injection. METHOD: Patients with acute myocardial infarction presenting up to 6 hour from the onset of chest pain were recruited for the study. Aspring(100-200mg) was given immediately. Total dose for 1.5mg/kg of rt-PA(minimum 75mg, maximum 100mg) was administered as triple bolus intravenous injections. The half of total dose was injected initially, the quarter of total dose was injected at 10 minutes after 1st injection and the remainder was injected at 40 minutes after 1st injection. Five thousand units of heparin was given and 1,000-1,500unit/hr was given continuously. Coronary angiogram was performed at 60 minutes and 7-10 days after the first bolus injection. RESULTS: At 60 minutes, eleven of fourteen patients (78.6%) showed TMI grade-3 of patency in infarct-related coronary artery. There were two patients of hemorrhagic complications. One patient developed cerebellar hemorrhage at third day after rt-PA injection, and the other developed bleeding at femoral sheath site. There was no in-hospital mortality and reinfarction. CONCLUSION: In patients with acute myocardial infarction, the simplified triple bolus injection of rt-PA is associated with high early patency(TMI grade-3) in infarct-related coronary artery, with low risk of major bleeding comlications comparable to other studies.