Satellite-derived total precipitable water (TPW) retrievals from both infrared (IR) and microwave (MW) sensors provide key information regarding atmospheric moisture content for use by field forecasters and numerical weather prediction centers which assimilate these products. These products are particularly important for providing this moisture information over the radiosonde-void, oceanic areas. The two products compliment one another nicely; the GOES TPW products are available every hour, but only over clear scenes, whereas the AMSU TPW products are available in all weather conditions (with the exception of heavy rain), but only four times (for two satellites) a day. The purpose of this study is to inter-compare time and space coincident GOES and AMSU TPW retrievals and to determine random and systematic errors associated with each. This information can then be utilized in a future step where the two products can be formally combined to generate a blended satellite TPW product. GOES-8, GOES-10, NOAA-15, and NOAA-16 TPW products for June-July 2001 will be collected and collocated for this study. A detailed statistical analyses and individual case studies will be presented.