OBJECTIVES: Scarce data is available on the economic burden associated with haemophilia B (HB). The aim of this study was to evaluate in a representative French HB population the impact on health-related quality of life (HRQOL) and to estimate the costs associated with its management. METHODS: EQOFIX is a prospective cohort study in patients with moderate and severe HB with one year follow-up. Data collected included: patients’ demographic and clinical characteristics, severity status, therapeutical approach, FIX consumption and all other resources used. Two types of HRQOL were used: generic (Kidscreen for children and SF-36 for adults) and specific (QUAL-HEMO, specific to haemophilia patients). The French national health insurance perspective was considered to estimate the average annual cost using official cost database. RESULTS: A total of 155 patients had been included by 27 centres, representing a coverage rate of 25% of the French global population suffering from severe and moderate HB: 104 adults (74 severe and 30 moderate) and 51 children (40 severe and 11 moderate). 30.4% of patients received preventive treatment; 60.4% were on-demand treatment. Severe HB adults reported significantly poorer HRQOL than the moderate subgroup mainly on physical components. No HRQOL difference was observed among children. The average annual direct cost was €95,619 (SD 83,142) with no significant difference between adults and children, but with a difference with severity status (3.3 times higher in severe vs. moderate HB, p<0.001). Substitutive therapy represented 90%, of the total followed by hospitalizations 6.5%. Even if the prophylaxis strategy lead to higher costs than an on-demand strategy (p<0.001), it allows avoiding haemorrhagic events and remains in acceptable cost-effectiveness range. CONCLUSIONS: To date, no economic burden of disease studies focusing only on HB have been published. The EQOFIX study provides an important source of economic information for health care payers.