This paper discusses the use of a novel tangential-flow, three-stage, countercurrent cascade ultrafiltration configuration for continuous purification of monoclonal antibody Campath-1H from simulated mammalian cell culture supernatant. The main limitation of conventional ultrafiltration based bioseparation, particularly when using a single-stage system is the trade-off between recovery and purity. The aim of this study was to try to improve both purity and recovery of the monoclonal antibody by using the novel cascade ultrafiltration system. Purification experiments were carried out with the three-stage cascade system as well as with single-stage and two-stage versions of the proposed system for comparison. The recovery and purification factor were both significantly higher with the three-stage system. The highest purity obtained using the three-stage cascade system was 85%. The experimental purity and recovery were compared with corresponding values obtained by simulation and found to be in reasonably good agreement. (c) 2007 Elsevier B.V. All rights reserved.