Intracoronary streptokinase (250.000 units over 60-90 min) was administered within 7.8 +/- 0.4 hrs after the onset of myocardial infarction symptoms to 85 patients, and intravenous streptokinase (500.000 units over 5-10 min) was given within 4.8 +/- 0.4 hrs to 46 myocardial infarction patients. Coronary angiography was conducted 1 to 3 hours after intravenous streptokinase administration. Coronary arterial reperfusion was achieved in 62% of patients in the former group, and in 66% in the latter one. Reperfusion was seen in 84% of patients in the first 3 hours after the onset of infarction, and in 60-66% at later dates. Hypofibrinogenemia did not become critical and persisted for one more day in cases of intravenous streptokinase infusions, as compared to the intracoronary route. Intravenous administration of 500.000 units streptokinase at the rate of 100.000-50.000 U/min is an effective and safe method for the treatment of myocardial infarction, and its prospective application in health practices appears quite promising.