In the manufacture of biological pharmaceuticals, the elimination of potentially infectious agents, such as viruses, is a critical component in the purification pro­ cess. Without sufficient virus clearance, regulatory agencies will not allow the purified pharmaceutical to be used in a clinical trial. In the production of mono­ clonal antibodies for therapeutic uses, a purification process must be capable of eliminating substantially more virus (3 to 5 logs more) than that is estimated in a single-dose-equivalent of unprocessed bulk [1].