Uranium mining areas in the United States are identified and briefly described, and the geologic, geochemical, and hydrologic factors associated with the various types of ore deposits are discussed. Uranium deposits that are now being mined or have recently been mined by solution-mining techniques are identified and briefly described; as well, deposits for which licenses have been obtained, but which thus far have not been mined, are listed. The techniques used in these processes of uranium extraction are described and discussed. The environmental impacts specifically associated with these methods of extracting uranium are identified, using examples from case histories of in situ mining operations. Impacts on groundwater are of the greatest concern, and problems associated with these impacts are discussed. The major adverse impact is contamination from the effects of lixiviant chemicals. Restoration to acceptable post-mining conditions is a major concern and technical problem. Existing or proposed technologies to prevent or to control pollution from in situ mining of uranium are identified and discussed, with emphasis on the problems associated with groundwater.