The serum of Vipera palaestinae contains a factor which neutralizes effectively all the hemorrhagic activities of its venom. Antibodies prepared in rabbits against the crude snake serum do not abolish its antihemorrhagic activity. The antihemorrhagic factor was purified from the snake serum by ammonium sulfate precipitation, Sephadex G-75 gel filtration, DEAE-cellulose chromatography and isoelectrofocusing. The purified protein shows one band in immunoelectrophoresis and in disc electrophoresis which strongly stains with the PAS procedure. It has no gelatinase or caseinase activity; it is digestible by trypsin and is stable at high temperatures and at pH's of 6·0-9·5. The neutralization capacity of the purified preparation is about 20 times that of the specific horse immunoglobulins. The molecular weight of the antihemorrhagic factor is about 80,000 and its isoelectric point is 4·7. These data, together with the failure to form precipitin lines in immunodiffusion tests, suggest that the antihemorrhagic factor of Vipera palaestinae serum is probably an albumin-like or α-globulin fraction rather than an immunoglobulin. The antihemorrhagic factor of V. palaestinae also neutralizes the hemorrhagic activity of the viperids Echis colorata and Cerastes cerastes.