A calculation has been made of the meridional circulation sufficient to transport heat between the radiational sources and sinks in the stratosphere (15-55 km) and mesosphere (55-80 km). Assuming that the principal heat sources are in the region of the equatorial tropopause and in the mesosphere over the summer pole, with the corresponding heat sinks near the polar tropopause and over the winter pole in the mesosphere, the main circulation patterns are found. Below 30 km there is rising air over the equator with outflow towards both poles and descent towards the tropopause in high latitudes in both hemispheres. At higher levels there is ascent over the summer pole and descent over the winter pole with a well defined flow towards the winter pole above 50 km and a more indeterminate flow pattern between 30 and 50 km. The order of magnitude of the speed of these circulations is m sec-' horizontally and cm sec-' vertically.The calculations were made for the solstices, equinoxes and mid-times between them and several particle trajectories were determined. The results are in agreement with many of the observed physical features of the stratosphere and mesosphere, particularly the distribution of tracer elements.