Data from the historical rocketsonde network demonstrate that significant cooling of the upper stratosphere and lower mesosphere (~30--60 km) occurred in northern midlatitudes of the western hemisphere and in the tropics during 1962--1991. The downward trend of temperature averaged over this layer was about -1.7 K/decade and temperatures were apparently modulated by the solar cycle with amplitude ~1.1 K. The trend was a function of height and somewhat larger in the lower mesosphere relative to the middle and upper stratosphere. ¿ 1998 American Geophysical Union