The dramatic hemorrhages, the effect of the disease on history through its presence in Queen Victoria's descendants, and the devastating role of therapeutic concentrates in the transmission of the acquired immunodeficiency syndrome (AIDS) have made hemophilia A the object of great medical, scientific, and public interest. The commonest hereditary coagulation disorder and a disease without ethnic or geographic limitations, its incidence approaches 20 per 100,000 male births¹–³. John Conrad Otto emphasized its inheritance as an X-linked disorder in his 1803 description of the disease in a New Hampshire family: “males only are subject to this strong affection . . . .