Concentration polarisation, cake formation and pore fouling lead to a performance loss of microfiltration membranes in terms of reduced permeate flux. Causes of these phenomena are varied and depend largely on components and properties of the feed suspension, the most common causes are summarised in this paper. Techniques to limit this reduction or retard fouling are available and are reviewed, the range of methods covered include feed pre-treatment, choice of membrane material, flow manipulation, the use of high shear, gas sparging and additional force fields. (C) 2002 Elsevier Science B.V. All rights reserved.