A review is given of the effect of the space environment on the external surfaces of satellites. The early development of thermal control materials in the 1960's and the 1970's is summarized. Selected recent results, based on flight experiments from the SCATHA satellite (P78-2) of the Space Test Program and the Space Shuttle, are reviewed along with Laboratory experiments designed to understand the often unexpected results of the flight experiments. The topics include long-term stability of thermal control materials, contamination, spacecraft charging, and the effect of oxygen atoms on materials. Several areas of future research are proposed.