The hemophilias are characterized as hereditary coagulation factor defects with a clinical bleeding tendency, a prolonged activated partial thromboplastin time and a normal prothrombin time. Hemophilia was first recognized in Talmud writings of the second century. It was forbidden to circumcise the sibling male of a male who had bled at circumcision. These ancient Jewish writings not only recognized hemophilia, but also recognized its mode of transmission from mother to son, as this law applied only to the same mother; the father could differ. 1 Hemophilia has experienced an extremely interesting history. All are familiar with the hemophilia gene in Queen Victoria and its subsequent spread into Spanish and Russian royalties. The disease was first noted in the medical literature in 1803 after being recognized by Otto, a Philadelphia physician. The name hemophilia, however, was not attached to these disorders until 1828, and it is credited to a German physician named Hopff. In the 1800s the diagnosis of hemophilia was established by demonstrating a positive family history and abnormal whole blood clotting time, which became the standard diagnostic criteria for hemophilia. In 1947, antihemophiliac factor (Factor VIII, AHF, or AHG) was recognized. 2 This began an era of active investigation into the nature of classical hemophilia and led to the development of efficacious therapeutic products.