This book presents the proceedings of a workshop entitled the "Handling of Timescales in Assessing Post-Closure Safety" of deep geological repositories for radioactive waste organised in Paris on 16-18 April 2002 and hosted by the French Institute for Radiological Protection and Nuclear Safety (IRSN). The main objective of the workshop was to identify and discuss approaches related to, and work done on, the timescales issue within national radioactive waste management programmes in the context of assessing post-closure safety. The timescales in question depend upon the half-lives and levels of activity of the radionuclides considered for disposal. These proceedings include the presentations made at the workshop as well as a summary of the discussions held.