To improve reperfusion, immediate percutaneous transluminal coronary angioplasty (PTCA) was considered after intravenous streptokinase (0.75 to 1.5 million U) was administered to 98 patients with acute myocardial infarction less than 4 hours after the onset of chest pain. Thirty-four culprit arteries were occluded (group A); 42 arteries were patent with residual stenosis of more than 70% (group B). Twenty-two patients had residual stenosis of less than 70% (group C); eight of these had severe disease of the remaining vessels. Group C patients were either treated conservatively or underwent bypass surgery. Immediate PTCA was attempted in 74 patients (32 in group A, 42 in group B) and was successful in 68 (92%). Emergency bypass surgery for acute occlusion after PTCA was required in two patients. Follow-up averaged 23 months (range, 16 to 47 months). Asymptomatic occlusion recurred in three patients. Restenosis occurred in five patients: four had early restenosis (one in group A, three in group B) and one had late restenosis (group B). These arteries were successfully redilated. Late reinfarction occurred in two patients. They were treated with intravenous urokinase and repeat PTCA. Elective bypass surgery was performed in three patients because of recurrent angina. They had severe three-vessel disease as revealed by control angiography. The mortality rate was 2.7% (two patients; one in group B had early reinfarction, and one patient in group A died suddenly after 17 months). Eighty-five percent of patients treated with PTCA alone remain free of symptoms. This approach has a high success rate and low morbidity and mortality rates. Long-term results are superior to thrombolysis alone.