This is an open-label multi-center Registry in patients with hemophilia B receiving BeneFIX. All patients who begin treatment with BeneFIX in European Union countries, will be eligible for participation. Patient demographics will be collected at baseline for all patients. A baseline FIX activity and Bethesda assay for inhibitor based on historical data should be recorded if available. Adverse events as defined in the protocol will also be reported on the appropriate forms. Data will be collected from patients on an ongoing basis to ensure that information is being captured for each patient being treated with BeneFIX.

Inclusion Criteria:

• Patients with Hemophilia B scheduled to begin treatment with BeneFIX are eligible for Registry enrollment

Exclusion Criteria:

All EU patients beginning treatment with BeneFIX