This document provides basic guidance on protection of humans and the environment from the hazards associated with deep geological disposal of high level radioactive wastes. It reflects the need for internationally harmonized criteria. It sets out a basic safety philosophy for use in planning such disposals, the main objective being the isolation of the radioactive wastes from the human environment for considerable periods of time. The safety principles contained in this book are generally consistent with the recent recommendations of the International Commission on Radiological Protection (ICRP) and the Nuclear Energy Agency of the OECD (OECD/NEA).