The influence of the modification by additives in the characteristics of several ultrafiltration polymeric membranes was studied. Three asymmetric membranes with similar pore size (molecular weight cutoff (MWCO) of around 30 kDa) but different materials and pore microstructures – polysulfone, polyethersulfone and polyetherimide – were used. Effects of two different hydrophilic additives on membrane structure and the resulting performance were compared to determine the material with the best antifouling properties. Polyethyleneglycol (PEG) and alumina (Al2O3) were employed as additives in the phaseinversion method, N,N-Dimethylacetamide and deionized water were used as solvent and coagulant, respectively. Membranes were characterized in terms of hydraulic permeability, membrane resistance, MWCO profile and hydrophilicity (by membrane porosity and contact angle). The cross-sectional and membrane surface were also examined by microscopic techniques. Membrane antifouling properties were analysed by the experimental study of fouling/rinsing cycles using feed solutions of PEG of 35 kDa. Permeation and morphological studies showed that the addition of PEG/Al2O3 results in formation of a hydrophilic finger-like structure with macrovoids, whereas the addition of Al2O3 results in the formation of a hydrophilic structure with a dense top layer with Al2O3 nanoparticles and a porous sponge-like sublayer. Furthermore, polyethersulfone/PEG/Al2O3 membranes displayed superior antifouling properties and desirable ultrafiltration performance. The authors of this work thank the financial support of CDTI (Centre for Industrial Technological Development) depending on the Spanish Ministry of Science and Innovation. The authors also thank the Center for Biomaterials and Tissue Engineering (Universitat Politecnica de Valencia) for contact angle measurements and BASF (Germany) and General Electric (United States) for supplying the polymers used. García Ivars, J.; Alcaina Miranda, MI.; Iborra Clar, MI.; Mendoza Roca, JA.; Pastor Alcañiz, L. (2014). Enhancement in hydrophilicity of different polymer phase-inversion ultrafiltration membranes by introducing PEG/Al2O3 nanoparticles. Separation and Purification Technology. 128:45-57. doi:10.1016/j.seppur.2014.03.012