In this diploma thesis the deformation behaviour of a cast cobalt-chromium alloy with a chemical composition of Co-24Cr-8W-3Mo (in m.%) as well as a forged Co-28Cr-6Mo alloy was characterized by high temperature deformation experiments. The influence of deformation temperature and strain rate on the flow behaviour was analyzed. For the investigation of grain refinement, single-stage isothermal deformation tests were carried out on a deformation dilatometer. The deformation experiments were carried out in temperature range between 1150°C and 1200°C with strain rates of 0.01 s-1, 0.05 s-1, 1 s-1 and 10 s-1 up to a true strain of 0.98. During the high temperature deformation dynamic recrystallization was observed for both alloys. Furthermore, a strong influence of the initial grain size on the structure development was observed. A comparison of the flow curves shows that in case of the Co-Cr-W alloy, the recrystallization initiates at comparatively higher plastic deformation due to the coarser initial structure. The flow behavior of the Co-Cr-W alloy was investigated by means of a constitutive analysis based on an Arrhenius approach. The calculated activation energy at the maximum yield stress is about 425 kJ/mol. In order to characterize the dynamic effects, extensive investigations were carried out by means of a light optical microscopy, scanning electron microscopy, electron backscatter diffraction and hardness measurements in addition to the deformation tests.