The evaluation of the influence of photocatalyst (TiO2 P25) loading, feed cross-flow velocity (v), transmembrane pressure (TMP) and feed pH on the fouling phenomenon of polyethersulfone micro-filtration (HFKG18 - 0.1 mu m) and ultrafiltration (UE10 - 10 kDa, UE50 - 100 kDa) membranes in a photocatalytic membrane reactor (PMR) is presented. Scanning electron microscopy, atomic force microscopy and laser scanning microscopy were applied for the observation of the fouling cake. The increase of the velocity v led to an increase of the permeate flux which was attributed to the formation of a thinner TiO2 layer. The permeate flux, the thickness and the roughness of the fouling layer depended on the TiO2 loading only at the first stage of the process. The increase of TMP resulted in a stronger flux decline caused by the increase of the fouling layer thickness. No permeate flux deterioration was observed in case of HFK618 and UE10 when TMP of 0.05-0.1 MPa was used. In case of UE50 exhibiting the highest pure water flux the fouling was the most severe. When the feed pH was changed to pH 3 or 9 the flux decline was much stronger than when no pH adjustment was done. (C) 2014 Elsevier B.V. All rights reserved.