The aim of this work was to compare the data on flux decline with time obtained with ultrafiltration experiments of polyethylene glycols (PEGs) performed under different experimental conditions (transmembrane pressures and crossflow velocities) and the theoretical predictions for these experimental conditions obtained with the model proposed by Ho and Zydney (2000). This model considers that two main fouling mechanisms, pore blocking and cake formation, can occur when macromolecules are ultrafiltered. In this work, flux decline predictions were achieved without using empirical parameters dependent on operating conditions. The fouling experiments were performed using monotubular ZrO2-TiO2 ceramic membranes with a molecular weight cut off (MWCO) of 15 kDa (Orelis, France). A 5 g/L PEG (35,000 Da molecular weight) aqueous solution was used as feed. The model does not accurately describe the fouling dynamics under every experimental condition tested. However, the best predictions were obtained for high transmembrane pressures (TMPs) and low crossflow velocities when the cake layer is more likely to form.