A committee of geologists and geophysicists was established by the National Academy of Sciences-National Research Council at the request of the Atomic Energy Commission to consider the possibilities of disposing of high level radioactive wastes in quantity within the continental limits of the United States. The group was charged with assembling the existing geologic information pertinent to disposal, delineating the unanswered problems associated with the disposal schemes proposed, and point out areas of research and development meriting first attention; the committee is to serve as continuing adviser on the geological and geophysical aspects of disposal and the research and development program. The Committee with the cooperation of the Johns Hopkins University organized a conference at Princeton in September 1955. After the Princeton Conference members of the committee inspected disposal installations and made individual studies. Two years' consideration of the disposal problems leads to certain general conclusions. Wastes may be disposed of safely at many sites in the United States but, conversely, there are many large areas in which it is unlikely that disposal sites can be found, for example, the Atlantic Seaboard. The research to ascertain feasibility of disposal has for the most part not yet been done. Disposal in cavities mined in salt beds and salt domes is suggested as the possibility promising the most practical immediate solution of the problem. Disposal could be greatly simplified if the waste could be gotten into solid form of relatively insoluble character. In the future the injection of large volumes of dilute liquid waste into porous rock strata at depths in excess of 5,000 feet may become feasible but means of rendering the waste solutions compatible with the mineral and fluid components of the rock must first be developed. The main difficulties to the injection method recognized at present are to prevent clogging of pore space as the solutions are pumped into the rock and the prediction or control of the rate and direction of movement. This initial report is presented in advance of research and development having been done to determine many scientific, engineering and economic factors, and, in the absence of essential data, represents considered judgments subject to verification.