A series of experiments has been carried out to determine the Log removal value (LRV) of MS2 bacteriophages suspended in various buffers (osmosed water, tap water, aqueous solutions of NaCl and phosphate buffer solution) during filtration through hollow fiber membranes made of cellulose acetate. Viral concentrations in permeate and retentate were determined using two different methods, namely plaque forming unit (PFU) counting, which reveals only infectious particles and quantitative RT-PCR which detects the total (infectious+inactivated) number of viral genomes regardless of their infectivity. From this experimental study, we propose guidelines for preparing the challenging solutions and measuring their concentration which ensure a reliable assessment of the membrane performance. (C) 2011 Elsevier B.V. All rights reserved.