The genes for Haemophilia B(factor IX) and Haemophilia A(Factor VIII) were identified in 1982 and 1984 respectively. Identification of the genes provided definitive carrier and prenatal testing using RFLPS and in some cases direct mutation detection. In 1989 recombinant Factor VIII became available and provided a safer replacement therapy for Haemophilia A. In 1992 an unique mutation involving an inversion in intron 22 in Factor VIII gene accounted for 50% of mutations in severe Haemophilia A further increasing accuracy of carrier and prenatal testing. But there still remains a 1-2% of cases where mutations are not found using existing technologies. Recombinant factor VIII and Factor IX have provided a safe replacement therapy for many years and now recently modifications of the proteins are improving the characteristics of treatment – eg longer acting products. Progress in gene therapy is now seeing success in haemophilia B with further experimental work continuing in Haemophilia A.