The authors study the biological variations which accompany an oral, thrombolytic treatment in which urokinase and lysyl-plasminogen are combined. Fibrinogen, the products of degradation of fibrinogen or fibrin, plasminogen and rapid alpha 2 antiplasmin are studied as a function of time. Two dimensional electrophoreses were carried out at precisely determined times. The combination of the two therapeutic agents causes the appearance of plasmin in the circulation, but it is neutralised by its rapid inhibitor. This therapeutic protocol entails moderate circulating fibrinolysis and may easily be monitored by determination of the circulating fibrinogen.