A number of studies over the past 20 years have demonstrated that the perfluorinated ion-exchange polymer Nafion is an excellent support for metal-complex catalysts. A variety of cationic metal-complex catalysts have been successfully immobilized in Nafion with little if any leaching occurring during catalysis, and in several instances the supported catalyst has been re-used with little loss in activity. Whilst the activity of Nafion-supported catalysts has been shown to be dependent upon catalyst loading, suggesting diffusion limitations, activities comparable with homogeneous activities have been observed by increasing the dispersion of Nafion. The physical structure and chemical properties of Nation offer the additional benefits of providing protection to the supported catalyst from deactivation and the potential to increase the activity of the supported catalyst compared with its homogeneous analogue. Although diffusion limitations and the high cost of Nafion have potentially limited its application as a metal-complex catalyst support. the recent development of high surface area Nafion-silica nanocomposites provides the opportunity to solve these issues.