Rock salt formations can make suitable hosts for the disposal of high-level radioactive wastes. The performance of salt as a host rock for a repository over million-year timescales has been investigated for the potential site for a geological repository at Gorleben in Germany. The main threat towards the stability of a natural salt barrier is its high solubility. Hence, prevention of water access into the waste emplacement area has to be ensured. Geological factors to be assessed in this context include diapirism, the formation of (future) glacial channels, the impact of loads and stresses imposed by glaciers, hydrocarbons, and the local hydrogeology. The disadvantages of salt are, however, outweighed by its beneficial properties: high thermal conductivity, good hydro-mechanical properties, and a tendency to creep and thus seal cracks. These characteristics make rock salt a very attractive candidate to host a geological repository for essentially all kinds of radioactive waste.