Coke formation in the Methanol-to-Gasoline reaction on commercial HZSM-5 zeolite was studied under various carrier gases. The rate of deactivation decreases in the order N-2 < H-2 < C-3/C-4 alkanes, which can be explained by assuming heterolytic dissociative gas adsorption on strongly acidic sites and cracking of coke deposits under the influence of the hydrogenation properties of the carrier gas. The methanol conversion at temperatures of about 690 K caused dealumination of the used HZSM-5. The Si/Al ratio increased from 80 to > 400. Despite dealumination no decrease of activity was found for regenerated zeolite catalyst indicating that methanol conversion needs only few acid sites.