In der vorliegenden Arbeit wird die Thermodiffusion von Oe02 in U02 untersucht. Es wird eine Anlage beschrieben, in der zylindrische Proben in einem Te=peraturgradienten zwischen 1400 und 2200°0 geglüht werden können. Die Oe02-Konzentration in den verwendeten Proben betrug 3.7, 5.6 und 13. Investigations of thermal diffusion of Oe02 in U02 are reported. An equipment is described in which cylindrical sampIes can be annealed in a temperature gradient between 1400°0 and 2200°O. The Oe02-concentrations in the used sampIes were 3.7, 5.6 and 13.3 wt %. The distribution ofOe02 after the annealing procedure in a temperature gradient was analysed by =eans of an electron microprobe unit. As the =ost important result it was established that the Oe02 migrates to the higher temperature by a thermal diffusion process. Thus, the Oe02-concentration decreases in the lower temperature range and increases in the higher temperature range. After annealing some days a minimum of Oe02-concentration at a temperature of 1700°0 and a maxiInum