The transformation of butanes over H-ZSM-5, Zn-ZSM-5, and Ga-ZSM-5 at 773 K were studied with special emphasis on the activation mechanism of butanes. Over H-ZSM-5, butanes undergo cracking exclusively by a carbonium-ion mechanism at low conversion levels. At higher conversion levels, the activation by a hydride-transfer mechanism are involved. The loading of Zn and Ga greatly enhances the dehydrogenation of starting alkanes as well as intermediate alkenes. The loading of the metal cations promotes also the cracking, especially in the case of isobutane. The synergetic action of the metal cations and protons is proposed as a mechanism of alkane dehydrogenation.