Between 1980 and 1992 there was a 70-fold increase in reported hepatitis B cases in British Columbia (BC), to a rate of 32 per 100,000 population, more than three times the national average of 10 per 100,000. In BC, this disease is one of young adults--less than 5% of reported cases occur under the age of 15 years. While Canada remains an area of low endemicity where transmission is mostly sexual or as a result of lifestyle choices, programmes of targeted immunization of certain high-risk groups (neonates of infected mothers, household and sexual contacts of acute cases and selected healthcare workers) begun in the mid-1980s have failed to reduce the increasing rate of reported infection. In September 1992, an expanded programme of hepatitis B immunization was implemented in BC. The programme has two main components: universal immunization of a cohort of pre-adolescent children in schools and broadened targeted immunization of groups at known elevated risk for transmission. The school-based programme involves provision of a three-dose series by public health nurses to all children in grade 6 (age 11 years) for whom parental consent is given. During the 1992-1993 school year, more than 42,000 grade 6 students were eligible for hepatitis B vaccine and the three-dose series was completed by 91% of students throughout the province.(ABSTRACT TRUNCATED AT 250 WORDS)