During the fourth quarter of 1997, a vaccination campaign using the meningococcal C polysaccharide vaccine was carried out in 14 autonomous regions of Spain. The remaining three regions did not participate. In the last quarter of the year 2000, a mass vaccination campaign using the meningococcal C conjugated vaccine was carried out in all regions. In the year 2001 the incidence decreased in all regions, although the decrease was greater in regions that did not vaccinate in 1997. In contrast, case fatality rates did not decrease. During 200 1, the incidence rate of meningococcal C disease was still lower (0.32 per 100,000 persons-year) in the regions that vaccinated in 1997 with the polysaccharide vaccine than in those that did not (0.64 per 100,000 persons-year). (C) 2002 Elsevier Science Ltd. All rights reserved.