Hemophilia A (deficiency in factor [F] VIII) and hemophilia B (deficiency in FIX) are the most common serious congenital coagulation factor deficiencies. (Based on strong evidence) Hemophilia is a genetic disorder inherited in an Xlinked fashion. Both diseases cause similar bleeding diatheses, with the hallmark being hemarthroses. (Based on strong evidence) The optimal treatment is recombinant factor replacement to prevent bleeding; however, this treatment has many barriers. (Based on strong evidence) The most serious complication of treatment is the development of inhibitors to factor products. (Based on strong evidence) Care for patients with hemophilia is most appropriate in a comprehensive care setting. (Based on strong evidence).