Radioactively contaminated sites often cannot be remediated to acceptable residual levels of contamination and released for unrestricted use. Residual contamination, buried wastes and other hazards may remain after cleanup is complete. Reasons for this include: technical limitations; economic feasibility; worker health and safety issues; or prevention of collateral environmental impacts. An optimum balance between social and economic cost and level of protection has to be found. Hence, maintenance of institutional control is likely to be required for very long periods of time. This publication discusses the relevant issues and approaches to tackle the conceptual, managerial and technical problems of maintaining institutional control over possibly hundreds or even thousands of years. These provisions and processes for maintaining institutional control over prolonged periods of time and for managing the radiological liabilities are often referred to as ‘stewardship’.