This Report examines international proposals for the underground storage of high level radioactive waste. From this study proposals have been developed in relation to conditions that can be expected in the United Kingdom. This Report is restricted to the consideration of repositories in the softer rocks, the clays and the shales which can be encountered in many parts of the United Kingdom. It has also considered the construction of a repository in rock salt. The only such deposits which could be developed for the purpose are found under the North Sea. For the purpose of this Study it has been assumed that suitable sites can be located near enough to a coast line to allow works to be constructed from the land. The likely cost of a repository will vary widely depending upon the nature of the ground in which it is constructed and the depth. The choice here is not an engineering matter but is dictated by the degree of protection which it is necessary to give to the environment, both within the forseeable future and for many generations to come. Costs are estimated making various assumptions.