From November 1995 to May 1996, a meningitis epidemic occurred in northern Nigeria. More than 75,000 cases and 8440 deaths (case fatality rate (CFR), 11%) were recorded. Médecins sans Frontières, in cooperation with the Nigerian government, carried out an assistance programme (support to case management, surveillance and mass vaccination) in three states (Bauchi, Kano, Katsina) where 75% of cases occurred. Cost analysis of this assistance in Katsina State reveals that case management and mass vaccination were efficient: US$ 35 per case treated and US$ 0.64 per vaccination. There was, however, a remarkable difference in cost-effectiveness between the two strategies. The cost per death averted by improved case treatment was estimated to be US$ 396, while the cost per death averted by vaccination was estimated to be US$ 6000. In large part this difference is attributed to the late start of vaccination: more than 6 weeks after the epidemic threshold had been passed. During meningitis epidemics in countries where surveillance systems are inadequate, such as in most of sub-Saharan Africa, curative programmes should have priority.