The stratospheric and mesospheric sounder (SAMS) on the NIMBUS 7 satellite is a limb sounder measuring infrared thermal emission from gases in the earth's atmosphere. Carbon dioxide measurements near 15 μm are used to determine the temperature profile and satellite roll angle. These temperature fields are compared with measurements by the NOAA 6 SSU and radio/rocketsondes over a 13-month period in 1980/81. Consistent patterns of bias between the instruments are found but are generally less than 2 K. Some of these are attributed to atmospheric tides, but others appear to indicate erors, including a problem caused by atmospheric ozone affecting lowe-stratosphere SAMS measurements. Remarkably good agreement is found between variations measured by the three sensors, with standard deviations of difference typically of 1 K and correlation coefficients of up to 0.994 over the whole period.