Abstract. With a detailed chemistry scheme for the middle atmosphere up to 70 km which has been added to the 3-D Karlsruhe simulation model of the middle atmosphere (KASIMA), the eects of coupling chemistry and dynamics through ozone are studied for the middle atmosphere. An uncoupled version using an ozone climatology for determining heating rates and a coupled version using on-line ozone are compared in a 10-month integration with meteorological analyses for the winter 1992/93 as the lower boundary condition. Both versions simulate the meteorological situation satisfactorily, but exhibit a too cold lower stratosphere. The on-line ozone diers from the climatological data between 20 and 40 km by exhibiting too high ozone values, whereas in the lower mesosphere the ozone values are too low. The coupled model version is stable and diers only above 40 km signi®cantly from the uncoupled version. Direct heating eects are identi®ed to cause most of the dierences. The well-known negative correlation between temperature and ozone is reproduced in the model. As a result, the coupled version slightly approaches the climatological ozone ®eld. Further feedback eects are studied by using the on-line ozone ®eld as a basis for an arti®cial climatology. For non-disturbed ozone conditions realistic monthly and zonally averaged ozone data are sucient to determine the heating rates for modelling the middle atmosphere.