This paper discusses an integrated one-step bioseparation technique for separation of human plasma proteins HSA and HIgG. This technique which was carried out in the pulse-input mode combined three separation processes, i.e. (a) in-situ ammonium sulfate induced precipitation, (b) microfiltration. and (c) membrane adsorption, all of which were carried Out simultaneously within the same membrane filtration device. The microfiltration membrane used in this technique retained HIgG by two mechanisms while the HSA was allowed to pass through the system unhindered. The antibody fraction precipitated by ammonium sulfate was retained by a sieving mechanism (i.e. microfiltration) while the antibody fraction remaining in solution was retained by hydrophobic interaction based membrane adsorption. Using this integrated bioseparation technique, nearly total separation of HSA and HIgG could be accomplished in just one step. The purity of the HSA and HIGG fractions obtained were both in excess of 96% while the recoveries were in excess of 95% each. (C) 2004 Elsevier B.V. All rights reserved.