The first purpose of this book is to provide a comprehensive review of the state of development of natural analogue studies with emphasis on those studies which are relevant to the following repository designs: Nagra (Switzerland) disposal concepts for high-level waste/low and intermediate-level waste; SKB (Sweden) disposal concepts for spent fuel/low and intermediate-level waste; and Nirex (UK) disposal concept for low and intermediate-level waste. The book's second aim is to discuss the expanding application of natural analogues for non-performance assessment purposes, especially their potential for presenting the concept of geological disposal to various interested audiences in a coherent, understandable and scientifically legitimate manner. Much of the discussion of the book is relevant to concepts for geological disposal of radioactive wastes by other countries, and is concerned only with those physico-chemical processes which control the release of radionuclides from the near-field, and their subsequent retardation and transport in the geosphere.