The viral safety of Chinese hamster ovary (CHO)-cell-based pharmaceuticals is well established. There have been more than 100 million infusions of CHO-derived pharmaceuticals without a single documented case of viral transmission. The recombinant factor IX (rFIX) process builds on this safety record by using a state-of-the-art multitiered approach to viral safety. This includes extensive testing of the CHO cells used to produce rFIX, routine viral monitoring of the cell culture production process, a manufacturing process and formulation that do not use blood or plasma products, and validation of the viral removal capacity of the purification process. The multifaceted viral safety program for rFIX has sufficient redundancy between approaches to compensate for potential limitations of any single safety measure. Together, the elements of the rFIX multitiered viral safety program offer patients and physicians a product that is inherently free of human blood-borne pathogens, including any risk of human immunodeficiency virus (HIV) hepatitis, parvovirus, and Creutzfeldt-Jakob disease (CJD).