Due to increasing use of whey proteins in functional foods and pharmaceutical products there is a need to develop processes to selectively separate and concentrate individual whey proteins. Existing methods for large-scale separation of whey proteins have included reverse osmosis, ultrafiltration, microfiltration and ion exchange. This study looked specifically at the use of synthetic microporous membranes, with functional groups covalently attached, to selectively separate β-lactoglobulm bovine serum albumin (BSA), α-lactalbumin, lactoferrin, lactoperoxidase and finally caseinomacropeptides from rennet whey. Initially strong cation exchangers and anion exchangers were considered, later this was expanded to include weak anion exchangers.