During animal experimental phase, lis-pg combined with UK produced a thrombolysis of about a 62.5%. This effect is accompanied by an important fibrinolytic system activation, a decrease in fibrinogen levels (0.37 +/- 0.2 gr/l) and an increase PDF/Fg (120.5 +/- 30 ng/ml). Such thrombolytic stage produced diverse hemorrhagic complications in experimental animals. During human clinical trial stage, then patients with Deep Venous Thrombosis (DVT) at proximal lower limbs level were submitted to diverse treatment protocols with Lis-Plasminogen (Lis-plg) and Urokinase (UK). After preliminary outcomes we can conclude that administration of Lis-plg followed by UK increases the fibrinolytic activity but also increases the risk of hemorrhagic complications. This second effect is not probably caused by an specific absorption on the thrombo surface, but by an increase of circulating plasminogen levels Lis-plg exogenous-induced.