Risk assessment can be thought of as the lens through which we anticipate the consequences of research and the impact of the actions of researchers. The way in which risk of harm is managed in research is strongly influenced by the surrounding social and political environment, leading to differences in national and local styles of regulation and review. Different research studies carry different risks, so systems for review and approval must adapt to the question being asked and the nature of the study. Researchers can never wholly guarantee safety in any research but participants and researchers must be offered reasonable protection within any study, with appropriate arrangements in place should something go wrong.