Ultrafiltration with diafiltration is a state‐of‐the‐art process used to separate solutions containing high and low molecular weight solutes. The focus of this paper is on the different concepts of ultrafiltration with diafiltration – batch, continuous and counter‐current – and the potential realization of diafiltration on an industrial scale in pharmaceutical biotechnology. Two case studies will be discussed from both technical and economical aspects.