To clarify virus removability from IgG solutions by Planova((R))20N, which is composed of cuprammonium regenerated cellulose hollow fiber membranes, we investigated the effects of virus spiking conditions as well as IgG concentration on the filtration performance (i.e. protein filterability and virus removability). The relationship between the performance and the membrane structure was also discussed. We used human IgG as the model protein and porcine parvovirus (PPV) as the model virus. The results revealed Planova((R))20N's IgG permeability at 5 mg/ml IgG concentration was independent of PPV spiking as well as PPV purity, and its flux decay was small. The filter also maintained a high virus logarithmic rejection value (LRV) (> 4) regardless of virus spiking conditions and filtration volume. For a wide range of IgG concentrations of 1-30 mg/ml, the flux decay was negligibly small keeping the high LRV. We consider these outcomes are due to the Planova((R))20N's unique membrane structure (i.e. the multi-layered, capillary-void structure, having the thick effective layer with high porosity), which enables a high virus trapping capacity (volume) with a low plugging rate of protein. These results indicate that Planova((R))20N has a well-balanced performance, eminently efficient viral removal capability and robust feature. (c) 2005 Elsevier B.V. All rights reserved.