Using a high-temperature Calvet microcalorimeter, we have studied the chemisorption process of methanol on alpha-Al2O3 at 200, 250 and 300 degrees C. From the measurement of calorimetric isotherms, volumetric isotherms and chemisorption differential heats, we have demonstrated the existence of Al sites of different strengths in alpha-Al2O3. At very low coverage of methanol, such active sites (q(diff)>200 kJ mol(-1), Lewis sites) are very strong and methanol is irreversibly adsorbed as methoxy groups by means of a dissociative mechanism, while at medium coverage, the sites are less strong (q(diff)>200 kJ mol(-1)) and methanol is reversibly adsorbed by means of a coordinative mechanism.