Some radioactive wastes arising at nuclear facilities have been stored for an extended period of time, often beyond the expected life of the storage vessels. IAEA Member States are moving forward with actions to retrieve such wastes for safe disposition. This publication covers the development of waste retrieval systems, with a specific focus on the safe removal and transfer of wastes which are in fluid form or which can be mobilized as wet or dry media. Detailed discussions are included of retrieval methodology, technologies and approaches. Extensive examples are provided from 21 waste retrieval projects completed or currently under way around the world, including lessons learned.