Synthetic membranes have become the focus of separation processes in different industries. Synthetic membranes may be composed of inorganic materials (such as ceramics) and organic materials (such as polymers). Current research on membranes focus more on polymeric membranes due to better control of the pore forming mechanism, higher flexibility, smaller spaces required for installation and lower costs compared to inorganic membranes. Though polymeric membranes have these properties which make them better materials in membrane fabrication, they also have some disadvantages which need to be overcome. Common problems faced by polymeric membranes, such as high hydrophobicity, exposure to biofouling, low fluxes and low mechanical strength have become the focus of researchers in order to improve these disadvantages. The incorporation of nanoparticles into polymeric membranes has been the trend in the field of membrane research recently. Incorporation of nano-sized materials could produce synergistic effects when incorporated with different types of materials. This paper discusses a few types of nanoparticles incorporated into various types of polymeric membranes. Nanoparticles that will be discussed include silver, iron, zirconium, silica, aluminium, titanium, and magnesium based nanoparticles. Nanoparticles affect the permeability, selectivity, hydrophilicity, conductivity, mechanical strength, thermal stability, and the antiviral and antibacterial properties of the polymeric membranes. Though nanoparticles usually improve the performances of the membranes, they also might change or even deteriorate the performances of the membranes. Thus, careful study needs to be done in order to choose the most appropriate types and composition of nanoparticles to be incorporated into polymeric membranes. (C) 2010 Elsevier B.V. All rights reserved.