Alumina-supported Pd, Au and Au-Pd catalysts were investigated for the simultaneous hydrogenation (HYD) of naphthalene (NP) and toluene (T) in the presence of dibenzothiophene (DBT). The nature of supported An, its resistance against S-poisoning when applied along with Pd in the hydrogenation of aromatics was studied. Additionally, the effect of two kinds of gamma-alumina (A(N) and A(S)) with different textural properties on the structure and performance of the catalysts was evaluated. Irrespectively of the support used, all the catalysts showed resistance to S-poisoning and their activity followed an order of NP > T > DBT. For hydrogenation of naphthalene, the specific reaction rates normalized to Pd loading follows trend: Au-Pd/A(N) much greater than Au-Pd/A(S) > Pd(A(N) > Pd/A(S). The higher activity in the hydrogenation of naphthalene of the separate Au-0 and Pd-0 phases on a type-N alumina support with respect to those supported on a type-S alumina was related to a more homogeneous dispersion of Pd-0 and Au-0 crystallites and a lower extent of coke formation. Under an excess of hydrogen the monometallic gold catalysts did not show any activity in the HYD of toluene. However, the An catalysts showed over-hydrogenation of NP to decalin, in contrast with the performance of the Pd and Au-Pd samples. This behaviour can be exploited to avoid the over-hydrogenation of naphthalene by using the bimetallic Au-Pd formulation. (C) 2004 Elsevier B.V. All rights reserved.