Proceedings of a symposium, Hannover, Germany, 3–7 March 1986. The purpose was to review advances made in the area of siting, design and construction of underground repositories for radioactive wastes and to consider developments of future importance. Forty-nine papers were presented, covering general approaches and regulatory aspects, disposal in shallow ground and rock cavities, disposal in deep geological formations and safety assessments. Contents: Keynote address: Are we ready to construct and operate an underground repository? General approaches and regulatory aspects; Disposal in shallow ground and rock cavities; Disposal in deep formations: Investigations on sites; Disposal in deep formations: Repository designs; Safety assessment; PaneI: Performance and safety assessments and their interactions with field investigations of deep geological repositories; Overview of symposium.