Permeate flux decline with time was estimated by means of a model [I] that considers gel layer formation as the main fouling mechanism. Several experiments were performed with two different membranes. Both of them were monotubular ceramic membranes. One of them was made of ZrO2-TiO2 with a molecular weight cut off (MWCO) of 15 kDa (Orelis, France) and the other was made of Al2O3-TiO2 with a MWCO of 5 kDa (Tami Industries, France). The feed was an aqueous solution of polyethylene glycol with a molecular weight of 35 kDa. All the experiments were carried out at the crossflow velocity of 1 m/s, when the cake layer is more likely to form. Transmembrane pressure (TMP) was varied between 0.1 and 0.5 MPa and the feed concentration was in the range of 5-15 g/L. The experimental results and those predicted by the model were compared for the experimental conditions tested. Model predictions were better for the Orelis membrane than in the case of the Tami Industries membrane under the same experimental conditions.