In the department of Puy-de-Dôme, France, 17 cases of invasive meningococcal disease C were notified between March 2001 and the first week of 2002. Among the 15 confirmed cases, 11 (73%) were serogroup C, 2 (13%) serogroup B, and 2 could not be identified. The rapid increase in the number of cases in a period of low endemicity for the rest of the country and the severity of the disease (case fatality ratio 27%, purpura fulminans 64%) led the health authorities to initiate a vaccination campaign targeting children and young adults from 2 months up to 20 years living in a limited area of the department. Around 80 000 people were immunised between 16/01/02 and 09/02/02. More than half of the 1390 immediate side effects were headache and dizziness. As of mid-March, no further case of meningococcal disease has been notified since 6 January.