Meningeal defects and primitive ENT infections are known to promote pneumococcal meningitis. Other risk factors can be identified in the occurrence of community acquired bacterial meningitis (CABM) and play a key role either in the frequency of this kind of infection, the type of bacteria concerned, the prognosis or the risk of recurrence. Thus, epidural infiltrations are rarely responsible for staphylococcal or streptococcal meningitis. Cochlear implants are also known to increase the risk of pneumococcal meningitis. The occurrence in children of aseptic meningitis or meningitis due to Staphylococcus aureus or Enterobacteriaceae is strongly suggestive of congenital spinal or cerebral anomalies (dermal sinus or spina bifida). MRI must be rapidly performed. In cases of splenectomy or asplenism, pneumococcal meningitis is common and must be prevented. According to the larger series available on this topic, age over 60, diabetes mellitus, alcoholism and immune deficiency are found to promote CABM in about 25% of cases. Streptococcus pneumoniae is the most frequent causative bacteria in elderly patients, in case of alcoholism, as well as Listeria monocytogenes and some Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae). L. monocytogenes is frequently isolated in immunodepressed patients and patients treated by anti-TNF molecules (infliximab notably). Finally, some genetic polyphormisms promote CABM: complement and properdin deficiencies (meningococcal meningitis), mannose-binding lectin deficiency, Fcgamma receptors alteration or interleukin-1 and IL-1R polymorphisms. Screening for such genetic disorders may be discussed in case of CABM but is mandatory in case of recurrent meningococcal infections.