Catalytic hydrogenation of 3,3,5-trimethyl-2-cyclohexen-1-one (isophorone) was examined over several supported noble metal catalysts in supercritical carbon dioxide. Charcoal supported rhodium and platinum catalysts were found to be active for the isophorone hydrogenation to 3,3,5-trimethylcyclohexanone (dihydroisophorone), but undesirable successive hydrogenation to 3,3,5-trimethylcyclohexanol also proceeded. Supported palladium catalysts were less active than the Supported rhodium and platinum catalysts, but were highly selective for dihydroisophorone. (C) 2003 Elsevier B.V. All rights reserved.