Epidemiological studies pose ethical problems, particularly concerning the confidentiality of identifiable personal data and the use of stored samples to carry out genetic and other tests. Ethics experts, national regulators, and international institutions take different stances on these issues. Intervention studies present particular challenges. Study protocols have to be approved by an ethics committee which aims to guarantee the protection of the subjects of the investigation. Committees rarely discuss how far a study responds to the health needs of the country where it is conducted. ‘Epidemiology between ethics and politics’ considers this issue especially relevant for developing countries, implying but going beyond ethics into the politics of research and health.