Summary: The effect of pre-irradiation of hexabromoethane with gamma rays upon subsequent thermal annealing of recoil bromine-82 has been examined: the doses given ranged from 2 to 2 X 107r. The results reveal a complex pattern which is discussed in terms of trapped defects having a variety of activation energies for release, and the interaction of the released defects with the recoil atoms. The results of both pre- and postirradiation (radiation annealing) were found to depend on radiation intensity. In the former case the higher the intensity the greater the effectiveness in promoting annealing while in the latter the reverse was true.