This report analyzes the work of research ethics committees (RECs)in the United Kingdom, which examine proposals for research on human subjects largely within the NHS. Research on human subjects throws up a variety of ethical problems. The role of RECs is essentially that of a public watchdog: to try to protect subjects from harm, to ensure that they are adequately informed, to see that valid consent is given, and that no undue pressure to participate is exerted among subjects, and to reassure the public that this is so. The research was carried out by a postal survey of members of RECs in England and Wales, as well as visits to 25 RECs, observing them in action, and interviewing their chairmen and members. The report describes the present position, examines the history of ethical review in the UK, and compares practice with current guidelines from the Royal College of Physicians and the Department of Health. The report, whilst making detailed recommendations for improvements to present practice, also recommends that there should be proper legislation.