The need for environmental friendly catalysts for alkane isomerization has prompted research on the WOx/ZrO2 system. Suitable promoters may improve its activity and stability. We investigated the effect of palladium on WOx/ZrO2 redox properties and catalytic activity for n-butane isomerization. Pd favoured the reduction of WxOy clusters already at RT (redox cycles O2H2) and in reduced samples EPR identified W5+ surface species. Increasing Pd dispersion increased the catalytic activity. Leached and pre-reduced catalysts resulted to have the highest activity, suggesting that the most active species are WxOy clusters anchored to zirconia surface and interacting with near Pd hydride. For n-butane isomerization I'd-promotion is as effective as Pt-promotion. (C) 2008 Elsevier B.V. All rights reserved.