Employing a quartz crystal microbalance and a quadrupole mass spectrometer in a vacuum chamber, thermogravimetric analyses (TGA) and mass spectrometer analyses have born performed at low temperature (90-190 K) on depositions of ammonia, acetone, methanol. toluene, isopropyl alcohol, water, para-xylene, and selected combinations of these materials. Deposition of a single species yielded a TGA curve characteristic of a pure substance. Homogeneous binary mixtures, like methanol and water, exhibited a desorption curve which contained structure in addition to that observed for the pure materials. Sequential layering of one material on top of another also altered the TGA response, suggesting substantial interlayer interactions, and the TGA curve shape was found to be a function of the top-layer thickness for the water-on-methanol system. Backfilling the chamber with nitrogen or argon at a pressure of 1 Torr increased the apparent desorption temperature of water by about 20 K.