Unlike most other coagulation factor deficiencies, usually associated with abnormal bleeding, lack of factor XII (Hageman) can result in thromboembolic events as a result of a deficient fibrinolytic system. We report a patient with an ischemic stroke and factor XII deficiency, a rare hereditary disorder. The optimal therapy for these uncommon disorders is not well established, but they probably require long term anticoagulation to prevent subsequent thrombotic events.