A method is developed for isolation of fibrinolytic and anticoagulant complex heparin-aspirin. The complex possessed the highest activity when the ratio of heparin to aspirin was 10 : 1. In vitro and in vivo the complex obtained showed high anticoagulant and fibrinolytic activity with respect to unstabilized fibrin both in absence and in presence of epsilon-aminocaproic acid as well as it had the thrombolytic effect on the fresh thrombus. The total fibrinolytic activity, nonenzymatic fibrinolysis and the anticoagulation activity in blood plasma were increased after chronic administration per os and after repeated intramuscular administration of the complex. The most distinct increase in fibrinolytic properties of blood occurred after intravenous administration of the heparin-aspirin complex.