[en] A review has been undertaken of the worldwide status of research and development related to the geological disposal of vitrified high level radioactive waste. The nature and quantities of vitrified high level waste that will arise from nuclear power generation in the UK have been estimated and considered. The safety case for establishing a geological repository would have to be based on predictive models, which could adequately represent the interactions and effects of a wide range of gradual processes and possible sudden events. No detailed repository design has yet been published, but the configuration currently favoured, in the UK and in most other countries, comprises a small number of vertical shafts, from which a network of horizontal tunnels would be excavated. Waste packages would be placed in holes drilled in the floors of the tunnels. The excavation of such a repository in hard crystalline rock, in a thick homogeneous formation of rock salt, or in the less plastic argillaceous formations, appears to be within the scope of present technology. Rock types available in the UK, which are likely to prove suitable for the accommodation of a repository, have been identified. The strategies and programmes for high level waste disposal in other countries have been reviewed. (U.K.)