Deep geological disposal is considered by many countries the best way of managing nuclear waste. Rock salt, granite, claystone, and other geological formations are already in use or being prepared for storage of radionuclides. Underground rock laboratories have been established for research purposes. Geologically old rock salt is a particularly suitable medium for permanent waste isolation and has a good record of performance in the USA. Issues arising from the presence of subsurface microbial life and storage of radioactive waste are reviewed here. Liquid forms of radioactive waste are the greatest portion of materials for disposal. Efforts for concentration of liquids include methods for adsorption of uranium and other radionuclides to microbial cells or cellular components. Another promising method is dissimilatory reduction of radionuclides by microorganisms, which increases the insolubility of nuclear waste and thus renders it more suitable for long-term storage. The capacities for remediation purposes of extremely halophilic bacteria and archaea, which are indigenous to rock salt, are just beginning to be explored. Nuclear transmutation - the fission of radionuclides by irradiation with fast neutrons into less harmful elements - is increasingly being developed by several institutions; however, the need for geological waste disposal will most certainly remain for many years.