Within the next 40 years, in the European Union approximately 11,000 t of metallic mercury has to be disposed that is no longer used in the chlor-alkali industry or is gained from non-ferrous metal production or the cleaning of natural gas. One disposal option is permanent storage in underground storage sites in salt rock. As a liquid, metallic mercury has been ex-cluded from this disposal option so far. Prior to a permit, it is necessary to investigate the par¬ticular challenges for the disposal practice that originate from the specific properties of me¬tallic mercury (liquid state, formation of toxic gases, laborious clean-up of contaminated areas). On the base of present knowledge a safe permanent storage of metallic mercury in under-ground storage sites is principally feasible.