Hepatitis B vaccine has been progressively introduced into the Gambian programme of immunization since 1986. Other African countries are considering introduction but require evidence of cost-effectiveness to justify such a decision. The cost of the Expanded Programme on Immunization in The Gambia, which includes hepatitis B vaccine, was calculated for 1988. Estimates of the effects of this programme on the incidence of liver cancer were made, based on the national cancer registry and a case control study of primary liver cancer and hepatitis B, regarding hepatitis B vaccine costs as incremental. This gave an estimate of the cost of averting a death from liver cancer in the range US$150-200 (assuming a vaccine cost of US$1 per dose). This indicates that universal hepatitis B immunization is comparable, in terms of cost-effectiveness, to other health interventions in less developed countries.