To evaluate the efficacy of intravenous streptokinase in acute myocardial infarction (AMI) 108 patients received a high-dose (1.5 million units), short-term infusion (60 minutes) within 6 hours after onset of symptoms, followed by anticoagulation. Before discharge a submaximal exercise test and a coronary arteriography were performed in 100 surviving patients. Sixty-seven patients had a patent infarct-related vessel. Clinical reocclusion occurred in 21 patients. Left ventricular function was slightly, but not significantly, better in patients with patent infarct-related vessels: ejection fraction 59.5 +/- 13% versus 57.4 +/- 13%. Additional procedures were performed in 20 patients: percutaneous transluminal coronary angioplasty (PTCA) in 8 and coronary artery bypass surgery (CABG) in 12. The results indicate that streptokinase applicated during a 6 hour-time window is a potent thrombolytic agent in acute myocardial infarction with limited effect on global left ventricular function. Pre-discharge evaluation is necessary to screen patients for residual ischemia.