Following experiments carried out on the Gleeble apparatus, tensile tests were performed on Grade C 85 WS steel specimens at temperatures of 800°, 1000°, 1240° and 1280°C, using a hot-stage microscope equipped with a tensioning device. The tests were carried out under brightfield and interference contrast-illumination and recorded cinemicrographically. The width of the image area was 400 and 800 µm, respectively. The film shows that the material remains ductile up to temperatures of 1240°C. Grain boundary slipping processes and sliding processes in the crystallites are to be seen in the course of the tensile tests. The processes taking place in the crystallites cause changes on the grain surfaces such as, for example, the formation of grain boundaries, shifting of grain boundaries, roughening and bulging of the surface. Hardly any deformation of crystallites occurs at the test temperature of 1280°C. Small amounts of liquid film from grain boundaries can be seen around the grain boundaries and these initiate fracture of the specimens without macroscopic deformation.