Basic aspects (coke deposition, acidity deterioration) of the deactivation by coke of a catalyst (prepared from a HZSM-5 zeolite) used in the transformation of aqueous ethanol into hydrocarbons in the 350-450 degreesC range have been studied. The experiments were carried out in an isothermal fixed-bed reactor with feeds of ethene, mixtures of ethanol and water at different mass ratios, and diethyl ether. The importance of temperature and water content in the reaction medium,on the mechanism of coke evolution is, demonstrated. The effect of these variables on deactivation is explained by a kinetic model in which the role of coke precursors (ethene, light olefins, and. gasoline) is considered. This role depends on the operating conditions, particularly the temperature.