During 1983-1990 in the Jiangsu province of China, 80,000 infants were randomised by area of birth between control, standard Hepatitis B vaccination (at 0, 1 and 6 months of age) and standard vaccination plus a booster dose at about 2 to 3 years of age. The aim is to prevent establishment of chronic HBV infection in early childhood, hence to prevent the morbidity of chronic hepatitis B in young adolescents and the incidence/mortality several decades later from liver cancer and other HBV related chronic liver diseases. Long-term follow-up through central registries will determine the impact of vaccination on liver cancer incidence and mortality.