A method for the preparation of a phospholipid-dependent prothrombin activator from the venom of snakes belonging to the Elapidae family, the activator comprising an increased plasma clotting activity in the presence of phospholipids and calcium ions; a reduced activity in the presence of Lupus Anticoagulant; an ability to facilitate clotting in a normal clotting time in the presence of platelet poor plasma, the plasma having normal or decreased levels of factor V, VII, VIII, IX, or X; and a major band with a molecular weight of 40,000 to 60,000 daltons on an SDS gel.