Eleven patients underwent thrombolytic therapy with streptodekase-1 and 19 with streptodekase-2. Of these, 11 patients suffered acute myocardial infarction, 10 had unstable angina pectoris, 6 thromboembolism of the pulmonary artery, 2 thromboembolism of the peripheral arteries and 1 thrombosis of the femoral vein. Administration of streptodekase-2 brought about an increase of the total blood fibrinolytic activity (the fibrinolysis time dropped from 248.8 +/- 82.1 to 137.5 +/- 42.5 min after 12 h), plasmin activation (from 0.00 +/- 0.00 to 23.5 +/- 7.5 mg after 24 h), reduction of the plasminogen content (from 94.0 +/- 2.5 to 46.8 +/- 5.3% after 12 h). The parameters of the coagulation hemostasis did not undergo any appreciable changes. Fibrinolysis activation following streptodekase-2 administration was unchanged within the first 48 hours. No material differences were identified in fibrinolysis activation in patients given streptodekase-2 and streptodekase-1. Administration of streptodekase-2 was found to exert a marked beneficial clinical effect on acute myocardial infarction, unstable angina pectoris, thromboembolism of the pulmonary and peripheral arteries.