In France, epidemiological surveillance of invasive meningococcal disease (IMD) is based on the analysis of reporting and mandatory reporting (MR) data, supplemented by microbiological characterization data for invasive strains. In 2005, 748 cases of IIM were reported, which corresponds, after adjustment for underreporting, to an incidence rate of 1.5 cases per 100,000 inhabitants. In 2005, 68% of cases were under the age of 20. The highest incidence rates were observed among children under 1 year of age (19.6 per 100,000), those aged 1–4 years (5.2 per 100,000), and those aged 14–19 years (2.8 per 100,000). Among the IIM cases for which the serogroup was known, 66% belonged to group B, 25% to group C, and 5% to group W135. The number of group B IIM cases increased by 16% between 2004 and 2005. The number of group C IIMs has been decreasing since 2003. The presence of purpura fulminans was reported in 29% of cases. The overall case-fatality rate (11%), which has remained stable since 2003, was higher in the presence (26%) than in the absence (4%) of purpura fulminans (p<0.001). The highest mortality rate was observed in those over 50 years of age for IIM B (19%) and in those under 1 year of age for IIM C (20%). Analysis of data since 2002 showed a positive impact on mortality from antibiotic administration prior to hospitalization in cases of suspected purpura fulminans (24% versus 33%, p=0.02). Evidence of meningitis [meningococcal isolation in CSF, Gram-negative diplococci on direct examination, or criteria associated with CSF suggestive of bacterial meningitis (cutaneous petechiae, soluble antigens, or positive PCR)] was found in 588 patients (78%). Evidence of bacteremia (meningococcal isolation or positive PCR in blood) or purpura fulminans was also found in 232 of these patients. Overall, after gradually increasing between 1996 and 2003 and then declining in 2004, the incidence of IIM rose slightly in 2005. This increase is primarily linked to serogroup B, whereas a decrease in the incidence of serogroup C has been observed since 2003. (R.A.)