One of the major limitations of the application of membrane processes in water and wastewater treatment is inorganic fouling. Despite the extensive studies on concentration polarization and inorganic scaling in membrane filtration, the fundamental mechanisms and processes involved in inorganic fouling are not fully understood. This paper critically reviews the mechanisms and models of concentration polarization and inorganic fouling in pressure-driven membrane processes. Effects of operating parameters and membrane properties on the formation of inorganic scale at the membrane surface are also evaluated. Future research areas that need to be pursued to alleviate inorganic fouling problems in membrane installations are discussed. (C) 2009 Elsevier B.V. All rights reserved.