Between 1999 and 2004, the European Union Invasive Bacterial Infections Surveillance Network (EU-IBIS) received c. 50,000 reports of meningococcal disease from 27 participating countries. Analysis has demonstrated a major decline in the incidence of invasive disease in those countries that have introduced routine vaccination against serogroup C infection. The establishment of rapid reporting of W135 and B2a/B2b strains has been able to provide early reassurance that these strains are not emerging as major public health problems in Europe. Between September 2001 and February 2005, the EU-MenNet project offered further opportunities for enhancing this data resource. Collaborative projects included: improving the EU-IBIS website; reviewing case ascertainment in Europe; reviewing cost-effectiveness studies for meningococcal serogroup C conjugate (MCC) vaccination; international comparisons of MCC vaccine efficacy; and mathematical modelling studies. In addition, linking of data from the European Meningococcal Multi-locus Sequence Type Centre to epidemiological data was performed. Particular clonal complexes were found to be preferentially associated with certain serogroups. Case fatality was also found to vary with clonal complex, suggesting that genotype can be a marker for hypervirulence. The importance of close collaboration between networks of epidemiologists, microbiologists, and the wider scientific and public health community is demonstrated.