Three ultrafiltration membranes, polyether-sulfone (PES), polyacrylonitrile (PAN) and cellulose acetate (CA) have been tested in order to study fouling and the removal of natural organic matter (NOM) from three natural source waters having different physical and chemical characteristics. The physically reversible fouling depended on the system of feed water and membrane type. Physically reversible fouling was significant for the system which consisted of hydrophobic feed medium-hydrophobic membrane (Las P, Lasek S - PES) as well as for the system: hydrophilic feed medium-hydrophilic membrane (Zabie D - CA). The change of membrane properties (the contact angles) after the filtration was observed. The foulants remained after physical cleaning render the PES and PAN membranes more hydrophilic, while CA membrane became more hydrophobic. The filtration cakes extracted from the membranes were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. According to spectra the water from Zabie D contained relatively more polysaccharide-like than protein-like substances, while the opposite relations between two groups were noted for Lasek S. The water form Lasek S demonstrated highest potential for fouling towards tested membranes. Las P sample showed more humic acid-like characteristics. (C) 2011 Elsevier B.V. All rights reserved.