We have successfully adapted an irradiation method for modifying poly(ether sulfone) (PES) membranes to reduce protein adsorption and mitigate membrane fouling, The method using ultraviolet (UV) radiation without a photoinitiator was previously developed with poly(arylsulfone) membranes. By choosing appropriate radiation and solution conditions, we have attached hydrophilic monomers (and resulting polymers) to the top portion of PES ultrafiltration membranes (top 15 mu m of total membrane thickness for 10 min irradiation). The resultant membranes were compared to the unmodified membranes using a standardized permeation test to obtain permeation flux and retention in the presence of a 0.1 wt% bovine serum albumin solution. Increased fluxes of about 20-27% with comparable retentions for the protein solution were obtained, The effects of solvent type (water or methanol), reaction period, and type of functional group were also measured. At 0.1 mg/l of BSA in solution, 43% less BSA was adsorbed onto the HEMA modified membrane than onto the original poly(ether sulfone) membrane.