Membranes are used extensively throughout the pharmaceutical and biotechnology industries for a wide range of separations. This talk will briefly trace the historical development of some of the key membrane bioseparation processes and will then focus on recent developments in membrane science and technology that are likely to have a significant impact in the coming years. Emphasis will be placed on showing how our improved understanding of the underlying transport phenomena have led to exciting new applications of membrane technology for bioseparations. Two examples will be highlighted: the development of electrically-charged membranes for protein purification and the use of ultrafiltration systems for the separation of plasmid DNA isoforms based on differences in flexibility. The use of electrically-charged membranes significantly increases the retention of like-charged proteins, providing the potential for highly selective separation of proteins with very similar properties. Membranes are particularly attractive in the large-scale purification of plasmid DNA for gene therapy and vaccines, overcoming the low capacities of chromatographic techniques. These developments have opened up exciting new opportunities for membrane bioseparations in the purification of high value therapeutics.