This thesis explores the way changing constructions of hepatitis B have mediated between science and policy during the past fifty years. Research-based 'facts' were filtered in the policy arena according to social, political and economic pressures. Central policy processes depended heavily on expert advisers, who emerged from networks of researchers. This account draws on scientific, clinical and epidemiological research, central policy documents, and interviews with people working with or suffering from the disease. Though epidemiologically close to AIDS, hepatitis B has rarely attracted public attention: there are an estimated 100,000 carriers in the UK, but few deaths due to the acute form. The disease was a major problem in the blood supply, and featured as a hospital infection, with notable outbreaks from 1965 in renal dialysis units. It was seen as an occupational hazard for laboratory workers, doctors, nurses and dentists. The introduction of a test for hepatitis B around 1970 opened up opportunities for epidemiological research. Hepatitis B was increasingly recognized as a sexually transmitted disease, widespread among gay men; also, because of needle sharing, prevalent among drug users. Another outcome of research in the 1970s was the development of a vaccine. However, availability of a vaccine in the UK from 1982 afforded no immediate resolution of public health issues raised by hepatitis B. The legacy of a restricted screening policy from the 1970s, emphasizing prevention via hygiene precautions among health care workers, facilitated a limited vaccine policy throughout the 1980s. While discussing negotiations over hepatitis B in the past five decades, this thesis aims to contribute to a broader analysis of interactions between science and policy, between centre and regions, and between interest groups.