Ultrafiltration is one of the most fascinating technologies, which has been introduced for application in the dairy industry. Ultrafiltration makes it possible to improve the quality of traditional dairy products, to create new food staffs, to utilize dairy by-products (such as whey) to a much greater extent for human nutrition and to prepare milk ingredients to be used in the entire food industry. In this study the application of ultrafiltration for milk and whey protein concentration, and research on nanofiltration for lactose concentration of the ultrafiltration permeate are detailed. The performance of ultra- and nanofiltration membranes can be characterized in terms of permeate flux, membrane retention and yield, which parameters are determined by pressure, recycle flow rate and temperature. The influence of these parameters on milk- and whey protein and lactose concentration was measured. The experiments were carried out using laboratory scale ultra- and nanofiltration units. The permeate flux, protein and lactose content in the permeate and in the concentrate fractions were measured during the experimental runs. Comparing the separation behavior of the membranes it was found that the investigated membranes are suitable for concentration of the milk- and whey proteins and lactose with high flux and retention. The filtration characteristics were obviously influenced by the process parameters. A new combination of membrane based cheese production procedure is proposed, which makes possible a significant increase in the cheese yield by incorporating the whey proteins. (C) 2004 Elsevier Ltd. All rights reserved.