Microwave limb sounding is a well-suited technique for the observation of the composition and temperature of the middle atmosphere. The Shuttle-borne millimeter-wave atmospheric sounder (MAS) measures three oxygen lines in the 61--64 GHz region. Since oxygen is uniformly mixed in the lower and middle atmosphere, the amplitude and shape of the emission lines depend only on temperature and pressure. From these oxygen emission lines, vertical temperature profiles are retrieved with a vertical resolution of 5 km in the altitude region of 15--45 km (127-1.5 hPa). The estimated total error is 1.5 K at altitudes of 25--35 km (24.5-5.7 hPa) and up to 5K above and below this region. Simultaneously with the temperature profile, certain instrument parameters are retrieved. We present the first MAS temperature retrieval results taken at three different locations from measurements of March 31, 1992, during the ATLAS 1 mission. The temperature retrieval results are basically in good agreement with National Center for Environmental Prediction (NCEP) analysis data, but the MAS retrievals have a tendency to low temperatures in the lower stratosphere. ¿ 1998 American Geophysical Union