Hemophilia A is an X-linked bleeding disorder caused by defective coagulation Factor VIII (FVIII). Although the efficacies of existing treatment using purified or recombinant FVIII are good, there remain shortcomings in using this particular form of treatment. A few FVIII gene therapy clinical trials have been initiated with modest improvements recorded, but these are no longer being continued due to insufficient efficacy. However, with the progress in the development of gene delivery vectors and the availability of mouse and canine hemophilia A models, gene therapy of hemophilia A remains an area of hot pursuit.