The most important requirements of thin film media for optical data storage applications as well as the most commonly studied write-once and erasable optical recording media were reviewed. Detailed optical properties and degradation characteristics of thin Te films were presented to illustrate some of these requirements. Both of these two material properties were shown to be strongly influenced by the film thickness, film deposition rate, and substrate due to their influence on the microstructure of the film. The degradation mechanism and the effects of humidity and temperature on the degradation rate of thin Te films were also reported and discussed. © 1985, American Vacuum Society. All rights reserved.