Membrane processes play a critical role in the purification of biotechnology products. Early membrane systems were adopted from technology originally developed for other industrial applications. During the last 2 decades, new membranes and modules have been developed specifically to meet the requirements of the biotechnology industry. This includes applications of membranes for sterile filtration, clarification, initial harvest, virus removal, protein concentration, buffer exchange, and protein purification. This manuscript provides an overview of recent developments in membrane technology, focusing on the special characteristics of the membrane systems that are now used for the commercial production and purification of recombinant protein products. Future developments in membrane technology are also discussed that may be able to meet the growing needs for higher productivity, lower cost of production, and increased development speed in the biotechnology industry. (c) 2007 Elsevier B.V. All rights reserved.