The grafting of vinylacetate (VAc) or hydroxyethylmethacrylate (HEMA) onto poly(vinyl chloride) (PVC) has been performed by means of γ-rays or chemical initiators. The grafted polymer so obtained has been separated by selective extraction and submitted to IR spectroscopy in order to check the amount of grafting. The grafting percentage was measured as a function of the grafting conditions. Using the above-mentioned polymer, dissolved again in DMF, asymmetric ultrafiltration membranes have been prepared by the phase inversion technique. The membranes have been tested with Dextran solutions. Their performances have been studied as functions of the grafting amount. The values of rejection and permeating flux demonstrated the effectiveness of the treatment in enhancing the performances of PVC ultrafiltration membranes.