Study Evaluating BENEFIX in Previously Treated Patients With Hemophilia B

Evaluation of Efficacy and Safety of Benefix®- Coagulation Factor ix, Recombinant, in Previously Treated Patients With Hemophilia b.

To assess efficacy and safety of BeneFix® for prophylaxis in "Short-term" therapy and on demand therapy for all bleeding episodes of subjects with hemophilia B.

Phase IV, open-label, non comparative, multicenter, previously treated patients (PTP) clinical trial. Patients with severe or moderate hemophilia B with baseline levels of plasma factor IX < 5% activity will participate in this study for both treatment regimens: "on demand" therapy for acute bleeding episodes and therapy for prophylaxis of bleeding episodes ( "Short-term therapy")*. * Short-Term Therapy: Prophylactic therapy given before surgery, including dental procedures, prior to a event that would likely result in bleeding ( sports, exercise, or heavy work), as well as to prevent further bleeds into a target joint). This short-term therapy for intermittent secondary therapy.

The primary variable will be the clinical response of BeneFix* in avoiding stopping or avoiding bleeding.

Inclusion Criteria: Patients with moderate to severe hemophilia B ( < 5% circulating factor IX activity) having acute hemorrhage or requiring "short-term therapy" for intermittent secondary prophylaxis regimens. HIV seropositive ( asymptomatic) or seronegative subjects. No history or detectable inhibitors.