Plasma products for therapeutic use pose specific challenges in manufacturing to ensure products maintain biologic activity and are safe with respect to contamination and transmission of disease-causing agents. Various processes have demonstrated effectiveness in eliminating, reducing, or inactivating viral contaminants. Recently, the possibility of transmitting variant Creutzfeld-Jakob disease (vCJD) or transmissible spongiform encephalopathies (TSE) through blood-based products has become a concern. The present study involves the validation of a hyperimmune immunoglobulin manufacturing process incorporating a nanofiltration step with a nominal pore size of 20 nm for removal of viral contaminants and other adventitious agents. Processing intermediates during the manufacture of IV Rh IgG (WinRho SDF/WinRho SDF Liquid, Cangene Corporation, Manitoba, Canada) were spiked with model viruses and processed in scaled-down procedures to validate the viral reduction capacity of each step. Anion-exchange chromatography and solvent/detergent steps are known to contribute to virus removal and inactivation. The Planova 20 N nanofiltration step was effective in reducing model viruses representing a wide range of viral morphologies with varying degrees of resistance to physicochemical inactivation. All in-process and final batch testing met current standards for production of IV Rh IgG manufactured with the previously licensed filter, which had a larger nominal pore size of 35 nm. The manufacturing process, employing a Planova 35 N filtration step, has been proactively improved by the change to a smaller-pore 20 N filter. Replacement of the 35 N filter with the 20 N filter produces a similar product while enhancing the capability for removal of smaller viruses and prions.