Abstract
The exponential increase in reported mutations within the factor VIII and IX genes in patients with haemophilia A and B has resulted in the use of several different systems for reporting such mutations. The Factor VIII/IX Subcommittee believe that a standardised reporting system will be beneficial to all interested in the field of haemophilia genetics. This article contains proposals for a mutation nomenclature based on general working practices and standardised to the present state of our knowledge of the sequence and structure of the factor VIII and IX genes.