Abstract German potash and salt mines have pioneered underground isolation of chemotoxic wastes. Comprehensive site-specific safety assessments have validated short- and long-term performance for each facility. Adherence to strict site prerequisites and waste-acceptance criteria combined with the reliance on enclosure inside multiple barriers justify confidence in the retention capacity of the total system. Underground waste isolation has been proven to be a success in Germany. Application of the lessons learned here will help solve environmental problems worldwide.