A defibrination syndrome developed in two men (aged 51, and 29 years old) within two hours of having been bitten by vipers Echis carinatus and Agkistrodon halys, respectively. In both the syndrome was characterized by afibrinogenemia with prolongation of the thrombin time, presence of fibrin monomers and split products of fibrinogen. Haemorrhagic signs included oral mucosa bleeding and macrohematuria. Specific serum was administered 9 and 16 hours, respectively, after the bite and achieved normalization of all clotting values within 48 hours.