Forty patients entering our hospital up to 12 hours (5.1 +/- 2.8 hours) after the onset of definite acute myocardial infarction were treated with accelerated streptokinase dose regimens (1.5 million U/30 min) intravenously. The reperfusion rate of infarct-related arteries determined by clinical evidence of reperfusion was 77.5% (31/40). There was significant difference in reperfusion rates: 89.3% (25/28) among patients within 6 hours versus 50% (6/12) among patients within 6-12 hours after the onset of chest pain. Five cases (12.5%) experienced mild bleeding complications. One patient had chill. Three patients (7.5%) had hypotension (BP < or = 10.7/6.67 kPa, 1 kPa = 7.5 mmHg). The 5 week mortality was 2.5% (1/40). In conclusion, intravenous accelerated streptokinase dose regimen for coronary thrombolysis seems to improve reperfusion rate markedly without increasing adverse events such as allergic reactions, severe bleeding and hypotension.