Bifunctional platinum over tungsten oxide promoted zirconia (Pt/WZ) and platinum over sulfate promoted zirconia (Pt/SZ) were characterized by XRD, Sg, ICP-OES, DRIFTS and test reactions: cyclohexane dehydrogenation (metallic function) and n-pentane isomerization (acid function). Both reactions were carried out at 300degreesC, atmospheric pressure and in the presence of hydrogen. Benzene and methylcyclopentane were obtained in the cyclohexane reaction and iso-pentane was the main product during n-pentane reaction. The poisoning with carbon disulfide (CS2) and n-butylamine (BA) of the two reactions, were measured. Pt/WZ and Pt/SZ were sensitive to both poisons used. CS2 affects directly the activity of the metal function and indirectly the one of the acid function because decreases the hydrogen dissociation capacity of Pt. BA only affects the acid function. (C) 2004 Elsevier B.V. All rights reserved.