Three known high activity hydrogenation catalysts, [RhCl{Ph2P(NC5H10)}(3)] (I), [Ir(C8H12)(PPh2Me)(2)]PF6 (II) and [Rh(C7H8){(Pr2P)(2)Fc}]BF4 (III, Fc = ferrocenyl), have been incorporated into Nafion by ion-exchange and/or ligand exchange methods, and the supported catalysts so obtained compared with their homogeneous equivalents for activity for hydrogenation of three substrates, cyclohexene, dimethylmaleate and 4-nitrotoluene. The catalysts retain their activity when supported in Nafion, producing yields of hydrogenated materials comparable or better than yields obtained homogeneously, with improved rates of reaction over those reported in other studies. (C) 2002 Elsevier Science B.V. All rights reserved.