The stress in platinum thin films was measured on microscope cover glass, fused quartz, and single-crystal silicon as a function of thickness at temperatures ranging from 100 ° to 600 °C. The stress had a high tensile value (≅1010 dyn/cm2) at 100 °C. It decreased sharply at 300 °C and was very small at 500 ° and 600 °C. A 1-MeV electron microscope was used to study the thicker films. For deposition temperatures of 100 ° and 300 °C and thicknesses below 1300 Å, the structure of the films was columnar with grains 100 Å in lateral extent. In addition, the platinum deposited on silicon above 300 °C showed some preferred orientation and formed Pt-Si compounds. The origin of a large tension in the films was consistent with a grain boundary model. The decrease in stress at 300 °C was ascribed to surface diffusion in the growing film. The low temperature data also correlated well with the flow stress calculations of Chaudhari, Mader, and Freedman.