Microfiltration is the oldest membrane process and shows up to now the largest market for technical membranes and membrane modules. In technical applications crossflow microfiltration is an established process for the separation of microparticles, bacteria and emulsion droplet. The following article describes the development and the state of the art. It makes a contribution to understand the mechanisms of crossflow filtration. (C) 2002 Elsevier Science B.V. All rights reserved.