Parvovirus retentive membranes made from polyethersulfone (PES) have been characterized by different techniques including dextran and phage retention. Results have been correlated with the pore size distributions of such membranes as obtained by liquid-liquid displacement porosimetry (LLDP). The results of LLDP concerning pore size distributions are proved to be consistent with those obtained by image analysis of SEM transversal sections and refer to the narrower pore section. Moreover, the maximum pore size determined by LLDP fairly correlates with the measured retention capabilities of the membranes. LLDP results suggest that the technique can be an accurate method for the determination of pore size characteristics of virus retentive membranes. This technique can be simplified to be even faster and straightforward by detecting only the maximum pore size of the membrane. (C) 2011 Elsevier B.V. All rights reserved.