Activated factor XII (FXIIc: Hageman factor) is a central component of the contact activation system of blood coagulation, fibrinolysis, and kinin formation. Although patients deficient in FXIIc (up to 50% of normal) do not show increased bleeding tendency, thrombotic complications were reported in 8% to 10% among these patients. The reduced generation of bradykinin resulting in diminished release of tissue plasminogen activator is proposed as a cause of thrombosis in factor XII (FXII)-deficient patients. Similarly, in patients with elevated levels of circulating antiphospholipid antibodies, hemostasis may be impaired resulting in excessive thrombophilia. Both vascular and placental thromboses because of antiphospholipid antibodies or FXIIc deficiency have been reported to be associated with recurrent fetal loss. We have experienced a case of factor XII deficiency in woman with recurrent spontaneous abortion. So we report this case with a brief review of literatures.