Percutaneous transluminal coronary angioplasty (PTCA) was performed in 21 patients with acute myocardial infarction (AMI) treated by intracoronary infusion of streptokinase within 8 h after the onset of symptoms. Streptolysis therapy began a mean of 3.6 .+-. 1.2 h (.+-. SD) after the onset of symptoms. The vessel was occluded in 14 patients and highly stenosed in 7. After the infusion of 67,300 .+-. 63,200 IU of streptokinase over 26.1 .+-. 21.5 min, patency of the occluded vessels was reached. PTCA as performed 20-60 min after the end of streptokinase treatment in 19 patients and 24 and 31 h after treatment in 2 patients. The dilation was successful in 17 patients (81%). The degree of vessel obstruction was reduced from 90.2 .+-. 7.3 to 58.6 .+-. 19.5% (area method) and from 71.4 .+-. 12.4 to 39.2 .+-. 19.7% (diameter method). The improvement was 31.5 .+-. 18.4 and 32.2 .+-. 19.3%, respectively. No reocclusion was induced by PTCA. Twenty patients were discharged. One died during hospitalization; at autopsy, the treated vessel was still patent. During the follow-up period, 2 reinfarctions and 1 asymptomatic reocclusion occurred. The clinical findings during the hospital course and the follow-up period were compared with those of a control group of 18 patients with AMI and comparable coronary stenoses who were treated only with streptokinase infusion. Four of these patients had a reinfarction during the hospital course, and 3 died during the follow-up period. PTCA can be performed safely and successfully immediately after the intracoronary infusion of streptokinase in patients with AMI. By reducing the subtotal stenosis, this treatment contributes to the reperfusion of the ischemic myocardium, diminishes the risk of a reocclusion and seems to improve the diagnosis.