Coronary thrombolysis by intracoronary and intravenous streptokinase (SK) is reported in myocardial infarction patients. Forty-two patients were examined within the first 6 hours of infarction: they were subjected to coronary-angiography on admission and 24 hours later, and their plasma fibrinogen levels were measured repeatedly for 2 days. SK administration was intracoronary in 24 patients and intravenous in 18. Rapid intravenous SK injection was not inferior to intracoronary administration in terms of efficiency. Although coronary reperfusion takes a somewhat longer time in cases of intravenous SK treatment, its technical simplicity and relative safety, as well as the fact that it can be started early suggest that it is a promising method of treatment for myocardial infarction.