This paper studies the total chemical energy release of seven exothermic reactions involving odd oxygen and odd hydrogen species at mesopause heights. Monthly and zonally averaged heating rates are calculated on the basis of atomic oxygen and atomic hydrogen densities as inferred from the SME satellite measurements in the altitude regime from 80 to 93 km. Trace constituents not available from SME were determined by means of a photochemical model. The resulting heating rates are found to be fairly high at all seasons, altitudes, and latitudes accessible to SME satellite measurements. Very large heating rates occur at high latitudes in early winter, reaching a maximum value of approximately 28 K per day. Consequently, chemical heating appears to play an important role in the energy budget and the dynamics of the upper mesosphere and lower thermosphere. ¿ American Geophysical Union 1994