Protein-A affinity chromatography is the standard capture technique used for purification of monoclonal antibodies (mAbs). A major problem with this technique is its inability to remove monoclonal antibody aggregates from the monomeric form of the antibody. Moreover, the elution of mAbs from a protein-A column is carried out using acidic conditions which in turn could accelerate the formation of antibody aggregates and causes leaching of protein-A from its supporting media. These impurities have to be removed using appropriate separation methods before the mAb can be used for therapeutic applications. There is currently a limited repertoire of polishing techniques which simultaneously remove both mAb aggregates and protein-A. In this paper, we describe a polishing method based on hydrophobic interaction membrane chromatography for simultaneously removing these impurities. The flow-through mode was used whereby monomeric mAb flowed through a membrane stack while impurities were retained by reversible adsorption. These impurities were subsequently eluted by lowering the salt concentration and the membrane stack was thus regenerated. The operating conditions for this method were systematically optimized using pure mAb, aggregates, protein-A, and mAb/protein-A complexes. The mechanisms by which aggregates and leached protein-A were simultaneously removed are hypothesized. (C) 2011 Elsevier B.V. All rights reserved.