Purpose ofthe Workshop In the spirit of enhancing developments in science and technology by facilitating international scientific cooperation, the Science Committee of NATO is sponsoring AR W's in several selected priority areas. The objective of this workshop was to discuss what microbial mediated problems have been experienced in the area of nuclear waste management and spent fuel storage. Long term storage of high-level wastes in repositories is just starting in some countries. However, low and medium level wastes have been stored for several decades. In the area of spent fuel interim, storage has been extended at many locations far beyond the intended time. It was a priority of the workshop to examine and discuss what deleterious effects have been observed under these storage conditions or under conditions used in simulated trial tests for predicting material performance under the storage conditions. For example, one chronic problem that was discussed was possibility that microbial influenced corrosion (MIC) could be taking place in the wet storage of spent fuel thereby initiating or accelerating the process of corrosion. Another discussion in the area of waste forms, focused on the presence ofbiofilms which may be breaking down the structure of the waste form and thereby jeopardizing its integrity. The meeting focused on discussing the observations and data collected relating to problems encountered in the storage of these types of wastes, and sharing this information with others that have not monitored their facilities for similar problems.