This is a long term study to evaluate whether hepatitis B vaccination in the first year of life will prevent primary liver cancer in adulthood. It is collaboration between The Gambia Government, the International Agency for Research on Cancer and the Medical Research Council in The Gambia. There is strong evidence that some 70% of hepatocellular carcinoma (HCC) in sub-Saharan Africa is due to chronic infection with the hepatitis B virus (HBV). In the early 1980s a vaccine became available that protected against both acute and chronic infection with HBV as judged by serological markers. This study was established because it was then unknown how long that protection might last and whether it would prevent liver cancer. The vaccination phase began in August 1986. Over the subsequent four years the vaccination was gradually introduced to immunisation teams on a team by team basis. This resulted in half the children born over these four years receiving hepatitis B vaccine (approximately 60,000) and half only receiving the other routine vaccinations. A second phase of assessment of the effect of vaccination on rates of infection with HBV began in 1997 with a cohort of 1000 vaccinated children who were followed until they were 9 years old compared to cross sectional samples of unvaccinated children at the ages of 5 and 9 years. These studies showed a high effectiveness of the vaccine against acute infection (90%) and in particular against chronic infection (95%). Two further cross sectional surveys of both vaccinated and unvaccinated individuals were carried out at age 15 years and 20 years respectively. These studies have shown that although the surface antibody induced by vaccination is no longer detectable in more than half of the individuals they continue to have 70% protection against infection and 95% protection against chronic infection. No case of acute hepatitis B has been seen in any vaccinated individual – all infections have been sub-clinical and only detected on serology. The third phase of the study consists of the identification of cases of HCC in the study groups and linked to their vaccination status. A national cancer registry set up by the study has been running in The Gambia since 1986. The quality of diagnosis and registration is not sufficient to provide an outcome to the study. Dr Ramou Njie (Hepatologist) leads recruitment of HCC cases and this will go on for between 5 and 10 years. It is estimated that a clear quantitative estimate of the protective efficacy of vaccination against cancer will be possible in this time. The enhancement requires extensive training, improvement in diagnostic facilities and quality of registration