BAX 326 (rFIX) Continuation Study

Main Inclusion Criteria: * Subject and/or legal representative has/have voluntarily provided signed informed consent * Subject has completed Baxter clinical study 250901 (pivotal study) or Baxter clinical study 251101 (pediatric study) * Subject was 12 to 65 years old at the time of screening for Study 250901 or \< 12 years old at the time of screening for Study 251101 * Subject has severe (FIX level \< 1%) or moderately severe (FIX level 1-2%) hemophilia B (based on the one stage activated partial thromboplastin time (aPTT) assay), as tested at screening at the central laboratory * Subject has not developed an inhibitory FIX antibody during Baxter Pivotal Study 250901 or Pediatric Study 251101 Main Exclusion Criteria: * Subject received factor IX product(s) other than BAX 326 upon completion of Baxter Pivotal Study 250901 or Pediatric Study 251101 * Subject has been diagnosed with an acquired hemostatic defect other than hemophilia B * For subjects transferring from Pivotal Study 250901: Subject's weight is \< 35 kg or \> 120 kg * Subject is planned to take part in any other clinical study, with the exception of BAX 326 Surgery study as described in this protocol, during the course of the Continuation Study