[en] Decommissioning and dismantling (D and D) of nuclear facilities are getting to be one of important issues of nuclear energy development in the world. The cooperative program on decommissioning has provided the chairing to exchange information on decommissioning and dismantling projects among the member countries of the Nuclear Energy Agency of Organization for Economic and Development (OECD/NEA) since 1985. The study on decommissioning cost was conducted by OECD/NEA in terms of cost items and variability of cost estimations among the D and D projects in 1990s. In progress of various D and D projects, it has been recognized that appropriate provisions have to be made in terms of policy, financing, and of management of the relatively large volume of materials arising from decommissioning. Under the circumstance, two groups have been set up by OECD/NEA to study recent problems; one group for cost and strategies, the other for safety and material management. These studies and information exchange on D and D projects are expected to be useful for D and D studies in Japan. (author)