These proceedings present the outcome of a conference on decommissioning and environmental remediation (D&ER) programmes, at which challenges, achievements and lessons learned in the implementation of such programmes during the past decade were shared and reviewed. The decision to combine D&ER in one conference reflects the significant synergies that exist between the two activities; the conference aimed to explore those synergies to foster and optimize the implementation of D&ER worldwide. Key goals were to raise awareness of the importance of addressing the legacies from past activities, to identify current priority needs and to provide recommendations on the strategies and approaches that can enable and enhance safe, secure and cost effective implementation of national and international programmes in the future. The conference was organized around seven themes: National policies and strategies; regulatory framework and standards; decision making process; technical and technological aspects; waste management; project management; and international cooperation. The publication provides a detailed synthesis of the presentations made and the panel discussions which took place during the conference. The main ideas and messages expressed and discussed at the conference are presented in the President’s report, which is included in the publication.