Radio wave absorption data for a large number of stations have been used to study the semiannual variations (SAV's) in the mesosphere. Temperature data for 50-km levels have also been utilized for a similar study. While the temperature data show a systematic variation for all latitudes investigated, the absorption data do not yield a systematic phase relationship with latitude. However, the maximum SAV is found to occur at the high-latitude station. The different behavior of SAV's with latitude could perhaps be explained in terms of mesospheric composition changes resulting from a SAV in the circulation pattern of the lower atmosphere.