Abstract: Hemophilia is a congenital hemorrhagic disease caused by genetic abnormalities in coagulation factor Ⅷ or factor Ⅸ. Current conventional therapy to prevent bleeding requires frequent intravenous injections of coagulation factor concentrates from early childhood. Hemophilia provides an attractive target for gene therapy studies, due to the monogenic nature of these disorders and easily measurable endpoints (factor levels and bleed rates). All successful, pre-clinical and clinical studies to date have utilized recombinant adeno-associated virus(AAV) vectors for factor Ⅷ or Ⅸ hepatocyte transduction. Although this is likely to alter the paradigm of hemophilia care in the near future, it will be important to overcome immune responses against AAV. This review focuses on current successes of clinical trials, and the future direction of hemophilia gene therapy.