This paper reviews methods of modifying polydimethylsiloxane (PDMS) polymers to improve their properties for biomedical applications. The modi®cation methods are discussed under three different categories: bulk, surface and other modi®cation techniques. Surface modi®cation techniques include physical and chemical techniques to modify polymer surfaces. Bulk modi®cation techniques include blending, copolymerization, interpenetrating polymer networks (IPNs) and functionalization. The third category includes less common modi®cation techniques.