Observations of upper tropospheric humidity (UTH) have become quantitatively much more useful in recent years due to a combination of improved understanding of the radiative transfer physics, improved numerical model initialization schemes, and improved computing and mass storage. In January 1996, the GMS-5 satellite was commissioned with an UTH channel and completing the addition of a UTH channel to all geostationary satellites. In order to extract quantitative climate signals from the data, however, they must be carefully calibrated and intercalibrated. Analogous with prior ISCCP calibration efforts, similar UTH channels on the polar orbiting satellites are used to provide a bootstrap vicarious calibration amongst all instruments. In order to perform this intercalibration, software was developed to optimize the matching of data from polar orbiting and geostationary satellites. Several different methods for intercalibration are examined and estimates of intercalibration accuracy and radiative transfer modeling accuracy are produced.