Pt particles supported on a physical mixture of alumina and HY zeolite were used in the hydrogenation of alpha-methyl-naphthalene (1-MeN) under conditions that approach industrial practice (P = 6 MPa; T = 498-548 K; WHSV = 1 h(-1)). As compared with the Pt/alumina catalyst, the use of the hybrid support markedly enhances the activity of the platinum catalysts. A maximum in the rate of methyl tetralin formation was found using platinum supported on a mixture of 3 wt.% HY zeolite in alumina; whereas, for the catalysts with higher zeolite contents, the rate decreased. Results of catalyst characterisation by temperature-programmed desorption (TPD) of NH3, IR spectroscopy of adsorbed CO and pyridine, H-2-chemisorption and X-ray photoelectron spectroscopy (XPS) revealed that methyl tetralin formation is favoured on bifunctional catalysts displaying moderate acidity. On the contrary, isomerisation and/or hydrocracking reactions of methyl tetralin are favoured in the more acidic catalysts containing higher contents (7% and 12%) of HY zeolite. (C) 2000 Elsevier Science B.V. All rights reserved.