Vinyl-functionalized polysiloxanes having different degree of branching, grafted on silica were used as hybrid supports for immobilizing the rhodium and platinum complex catalysts. The attachment of the metal species to the polymer was confirmed by IR and H-1 NMR spectroscopy. Both Rh and Pt supported systems effectively catalyzed the hydrosilylation of terminal olefin. The catalyst activity was found to be dependent on the type of a parent complex, the degree of polymer branching and the vinyl ligands content. The stability tests performed during the repeated use of the catalysts indicated a decrease in catalyst activity. (C) 2003 Elsevier B.V. All rights reserved.