Hemophilia is a genetic bleeding disorder that affects more than 15,000 Americans, most of whom are male. Currently, the disorder is spread equally across races and socioeconomic levels. It results from a genetic defect in the body's ability to produce one of the clotting factors. When blood vessels are injured, bleeding may occur. Significant quantities of these clotting factors must be present in the blood for it to clot. If one of these clotting factors is missing or present only in small quantities, it will take longer for the bleeding to stop.

The most common forms of hemophilia result from deficiencies of clotting factors VIII or IX. Both major factors VIII and IX are necessary to form a clot. At present, genetic control of the production of factor VIII and IX coupled with synthetic (recombinant) DNA technology have increased the level of purity and safety in factor concentrates, benefiting both current and future generations of hemophilia patients.

Hemophilia was first documented by the Jewish Talmudic writings in the second century. Later in the 1800s Queen Victoria passed the disorder to her descendents.