The Microwave Sounding Unit (MSU) on board the National Oceanic and Atmospheric Administration (NOAA) polar-orbiting satellites were designed to measure the atmospheric temperature from the surface to the lower stratosphere under all weather conditions, excluding precipitation. Although the instrumental design and calibration were made primarily for monitoring the atmospheric weather processes, the MSU observations have been extensively used for detecting climate trend. However, calibration errors have been a major uncertainty in climate trend detections. In order for the MSU data to be of high quality for climate trend and variability research, we have recently recalibrated the MSU satellites NOAA 10, 11, 12, and 14 using simultaneous nadir overpass (SNO) method. The calibration results in a well-merged 20-year radiance dataset for the MSU channels 2, 3, and 4. Limb-correction is applied to adjust the incident angles of the footprints. The limbcorrected radiances are further binned into 2.50 longitude by 2.50 latitude grids to generate deep-layer temperature datasets for the mid-troposphere (T2), tropopause (T3), and lower-stratosphere (T4). The global ocean averaged trends for the recalibrated T2, T3, and T4 are respectively 0.234±0.071 K/decade, 0.079±0.085 K/decade, and -0.414±0.287 K/decade for the 20-year time period from 1987 to 2006. Both the recalibrated radiance and deep-layer temperature datasets are freely available through the NESDIS/STAR website http://www.orbit.nesdis.noaa.gov/smcd/emb/mscat/mscatmain.htm htm.