ABSTRACTThe corrosion resistance of container materials in underground repositories is an important issue for the safe disposal of High Level Nuclear Waste (HLNW). The reliable prediction of container degradation rate and engineering barrier integrity over extended periods, up to several thousands years or even several hundreds of thousands of years, represents one of the greatest scientific and technical challenges. The first and the second International Workshops on Prediction of Long Term Corrosion Behaviour in Nuclear Waste Systems, which were held in 2001 (Cadarache) and 2004 (Nice), sought to compare the scientific and experimental approaches that are being developed in various organisations worldwide for predicting long term corrosion phenomena, including corrosion strategies for interim storage and geological disposal. The lessons learned during these Workshops, include the necessity of developing two approaches based on semi-empiricism and determinism in a complementary manner for effective prediction. The use of archaeological artefacts to demonstrate the feasibility of long term storage and to provide a database for testing and validating modelling work was also emphasized.