Summary. That gene therapy offers the promise of a cure for haemophilia was apparent more than a decade ago. After years of failure, substantial progress in the efficiency of gene transfer technology has recently resulted in impressive success in animal models with haemophilia. However, fears of the risks intrinsic to such therapy have been raised by the fate of two children cured of immune deficiency by gene transfer who have, however, subsequently developed leukaemia as a result of insertional mutagenesis. The purpose of this review is to outline the current status of gene therapy in light of recent successes and tragedies and to consider the prospects for curing haemophilia in the short-to-medium term.