The aim of this study was to evaluate, in economic terms, the recently launched hepatitis A vaccine in comparison with the use of nonspecific immune globulin, for the prevention of hepatitis A. A cost-effectiveness analysis was performed, comparing mass and selective strategies for both active and passive immunisation in children, adolescents and the high-risk adult population. Direct costs of diagnosis, treatment and immunisation, and travelling expenses of the individuals, were considered. The alternative of mass vaccination for children and adolescents cost 2679 to 6394 European Currency Units (ECU) [$US 3040 to $US 8312; 1994 values] per case prevented. Selective vaccination of high-risk individuals cost ECU205 per case prevented for young adults (those aged about 20 years) when the annual risk of contracting the disease was 0.7%, while there were net savings for all age groups when there was a 2 to 3% risk. The most sensitive variables affecting the cost of mass-vaccination strategies were incidence of hepatitis A, vaccine coverage and vaccine cost; for the various high-risk groups, these were vaccine cost, incidence of hepatitis A and costs of treating infection. Selective vaccination, depending on the age of high-risk patients [mainly travellers to endemic areas for periods of over 6 months, or those under 'precarious' conditions (e.g. backpackers, even for short periods)], is the most efficient alternative; in fact, the cost-effectiveness ratio has not been calculated, since there were net savings. For occasional travellers (as above, and those travelling for periods of under 6 months in 10 years), passive immunisation is more efficient. Selective vaccination for package-tour, short-stay travellers (infection risk around 0.3%) and strategies for mass vaccination of children and adolescents are not justified from an efficiency point of view.