Hemophilia is a common X-linked coagulation disorder due to deficiency of factor VIII. The factor VIII gene has been cloned in 1984 and a large number of mutations that cause hemophilia A have been identified in the last decade. The most common of the mutations is an inversion of factor VIII that accounts for nearly 45% of patients with severe hemophilia A. This review lists all the factor VIII mutations identified to date and briefly discusses their functional significance.