Abstract: A new catalyst, especially for the dehydrogenation of dehydrogenatable C.sub.2-30 hydrocarbons. The catalyst comprises a carrier consisting essentially of a mixed oxide of magnesium and alumina Mg(Al)O, and also comprises a Group VIII noble metal, a Group IVA metal and optionally a Group IA alkali metal. The catalyst may be subjected to a pretreatment comprising a reduction, a subsequent oxidation and finally a second reduction. The catalyst is particularly suitable for the dehydrogenation of C.sub.2-5 paraffins to olefins, with and without simultaneous oxidation of hydrogen.