OBJECTIVES: Multiple recombinant coagulation factor VIII (rFVIII) options exist in Europe for hemophilia A (HA) while only one recombinant factor IX (rFIX) has been available in hemophilia B (HB) until recently. While patients appear to switch between treatment options, reasons for this are not well described. This analysis compares the reasons for switching treatment among HA and HB patients. METHODS: The Cost of Haemophilia across Europe – a Socioeconomic Survey (CHESS) study is the first comprehensive cost-of-illness study in severe HA and HB (factor level <1%, >18 years) in France, Germany, Italy, Spain, and the United Kingdom. Physician-recorded data were collected for 1,285 individuals from January-April 2015. HA and HB individuals were grouped by recombinant or plasma treatment and assessed for reasons for switch as well as how their care could be improved. RESULTS: Among 84 HB individuals previously on rFIX, 15.5% switched to pdFIX and one to another rFIX. Reasons for switch included inhibitor development (21.4%), lack of efficacy/poor half-life (14.3%), patient request (21.4%), temporary use during hospitalization (35.7%), or other (7.1%). In contrast, the majority of HA switchers (n=217) switched to another recombinant FVIII (82.0% vs 18% for pdFVIII). Reasons for switches between rFVIII products included inhibitor development (12.8%), lack of efficacy/poor half-life (8.5%), product availability/reimbursement (31.9%), patient request (12.8%), tolerability/side effects (10.6%), temporary use during hospitalization (14.9%), or other (8.5%). HB individuals currently on rFIX therapy reported (n=31), more effective healthcare provisions (71%) and better availability of new products (45.2%) would improve their care. CONCLUSIONS: Results suggest that HA individuals switch treatments for efficacy or tolerability issues, among other reasons and most switch to another rFVIII. Introduction of new rFIX options may provide individual’s with HB the same freedom to switch to therapies to achieve their treatment goals.