We performed different "in vivo" investigations to study the pharmacological properties of a native DS: anti-thrombosis by the stasis model, bleeding potential by tail transection bleeding time and template bleeding time, and profibrinolysis by a growing thrombus model and by an established thrombus model. The results suggest that DS is a safe antithrombotic drug by i.v. administration without bleeding potential, even at very high doses (up to 16 mg/Kg). DS has shown a protective index of at least 4 in contrast to heparin that has shown a protective index of 1. The profibrinolytic models so far studied did not evidence a clear profibrinolytic contribution to the antithrombotic properties of DS, but showed a prolonged antithrombotic action that cannot be explained only by the heparin cofactor II potentiation.