Duteplase, 98% double-chain recombinant tissue-type plasminogen activator, was administered intravenously in 488 patients with acute myocardial infarction in a multicenter, open, safety and patency study. Duteplase dosing was based on body weight. Duteplase was administered as a bolus of 0.04 MIU/kg of thrombolytic activity followed by 0.36 MIU/kg over 1 hour and 0.067 MIU/kg/hour for 3 additional hours. The patency rate of the infarct-related artery at 90 minutes was 69% (330 of 478). The reocclusion rate at 3 to 48 hours was 6% (18 of 301). Reinfarction occurred in 7.6% of patients (37 of 488), but 12 reinfarctions occurred after coronary angioplasty. Serious bleeding occurred in 7.6% of patients (37 of 488), predominantly at the catheterization entry site. There were 3 instances of central nervous system bleeding, 1 fatal. Fibrinogen levels declined to 83% of baseline at 24 hours. Weight-based dosing may explain the low incidence of serious bleeding in this study. The in-hospital mortality was 6.6% (32 of 488). This study documents that the dose of duteplase used in the International Study of Infarct Survival-3 results in a 90-minute coronary artery patency rate and safety profile comparable to those reported in published studies on the approved dose of alteplase.