Early bypass grafting following intracoronary thrombolysis with streptokinase may be indicated in patients with acute coronary artery thrombosis and severe coronary disease. To evaluate this approach, we prospectively studied 41 patients (32 men and nine women, mean age 53 years) with acute infarction. Emergency cardiac catheterization was performed within 18 hours after onset of chest pain and intracoronary streptokinase was given. All patients underwent bypass 3 to 10 days later (mean 7 days). Serial gated radionuclide left ventricular angiograms to determine ejection fraction were obtained on hospital admission, preoperatively, and 3 to 6 months later. Thirty-four patients had complete occlusion of the artery supplying the infarcted segment. In 30 patients (88%) reperfusion was not successful. In seven patients the artery was not totally thrombosed. Thirty-two patients (78%) had multivessel disease. An average of 2.8 grafts per patient were placed with an operative mortality of 2% (one patient). Serial measurements of ejection fraction were obtained in 23 patients in whom the admission ejection fraction was less than 50%. There was a significant increase in ejection fraction from admission (33% +/- 11%) to the preoperative measurement (41% +/- 9%, p less than 0.001), and this improvement persisted at follow-up (40% +/- 14%). Intracoronary streptokinase has been shown to restore blood flow to infarcting myocardium and to improve left ventricular performance. In patients with significant organic stenosis, the risk of bypass grafting 3 to 10 days after intracoronary streptokinase infusion appears to be no different from the risk of elective operation performed at a time remote from an acute infarction.