After successful intracoronary and intravenous thrombolysis in acute myocardial infarction in about 90% of all cases highgrade organic stenoses of the diseased vessels can be found. These obstructions may impede coronary blood flow and be the reason for recurrent angina in the rehabilitation phase. In a prospective, controlled, randomized study with 127 patients (pts) with acute myocardial infarction 64 pts were treated with streptokinase (group I) and 63 pts were treated with streptokinase and additional PTCA procedures (group II). The patients of both groups did not differ with respect to age, distribution of sex and diseased vessels, time between onset of symptoms and start of lysis or time to maximum of CPK-curve. In group I 59 out of 64 pts had recanalized vessels (92%), in group II 56 out of 63 pts (89%). In 55/56 pts PTCA was attempted (success rate 65%) with an artificial reocclusion in two pts (4%). After four weeks in group I 47 pts were controlled angiographically. The stenosis rate did not differ between the acute phase and the control study (78.6 +/- 11.8% vs. 78.0 +/- 15.2%). Five reocclusions had occurred. In group II the resting stenosis after thrombolysis (81.7 +/- 6.6%) was diminished by PTCA to 33.0 +/- 18.2%. In the control study the remaining stenosis was 31.9 +/- 24.4%. The difference between groups I and II at the four week control was highly significant (p less than 0.001). In group I there were ten deaths during the hospital phase, nine of them of cardiac origin. In group II nine pts died, three from shock lung and five from cardiac causes.(ABSTRACT TRUNCATED AT 250 WORDS)