The residual stress in thin films formed by vacuum sublimation of bulk silicon monoxide has been studied as a function of source temperature, residual gases present during deposition, and exposure to atmospheric air after preparation. Highly stable films of silicon monoxide having a tensile stress from 2 to 5×108 dynes/cm2 can be prepared at system pressures less than 5×10-6 torr and at source temperatures between 1300 and 1400°C. If higher source temperatures are used, the resultant films anneal with time and are susceptible to cracking. Those produced at lower source temperatures are under a high tensile stress unless a high partial pressure of water vapor or oxygen is present. In this case oxidation occurs resulting in a decrease in the film stress. For completely oxidized films, a compressive stress of 3×108 dynes/cm2 was observed. Partial oxidation results in a film which is highly unstable in air. High partial pressures of carbon monoxide, carbon dioxide, nitrogen and hydrogen were found to have very little effect on the residual stress. © 1962.