Meizothrombin (MT) is one of prothrombin derivatives which appears in haemostasis activation area. However, its role in haemostasis regulation isn't clear. We studied the role of MT in fibrin formation, platelet activation and aggregation. A new effective method of obtaining MT from native human prothrombin was developed using immobilised prothrombin activator from Echis multisquamatis venom. The protein was stable and electrophoretically pure. Platelet-rich plasma for aggregation study and gel-sieved platelets for flow-cytometry were separated from blood of healthy donors. It was shown that MT transformed fibrinogen to fibrin and activated clotting factor XIII. MT didn't activate gel-sieved intact platelets, but in platelet-rich plasma, increased platelet aggregation induced by ADP, collagen and adrenalin.