Chlorinated polyvinyl chloride (CPVC)/polyvinyl pyrrolidone (PVP) membranes were prepared using the water vapor induced phase separation technique. The surface pore size of the membrane was dependent on the relative humidity (RH) and the PVP content. PVP was used as the pore-forming and wetting agent. However, as PVP could leach during the filtration process, the PVP was immobilized within the CPVC membrane by chemical cross-linking. This reduced the depletion of PVP from the membrane and maintained the hydrophilicity. The physical properties of the membranes were investigated before and after cross-linking using FT-IR, TGA, and contact angle measurements. The pure water flux of the membranes was measured using a filtration apparatus, and the quantity of PVP extracted from the prepared membranes was measured using a total organic carbon (TOC) analyzer. PVP immobilized on the microporous CPVC membranes showed an increased hydrophilicity and thermal resistance at a slight expense in water flux rate. This was confirmed by capillary flow porometry where the decrease in mean pore size of the membrane caused a decrease in water flux after cross-linking. (C) 2003 Elsevier Science B.V. All rights reserved.