A 39-year old male patient with a history of four episodes of meningitis (two of them due to Neisseria meningitidis) since the age of 12 developed meningitis caused by an ungroupable streptococcus. Deficiency of the sixth component of complement was discovered, making this the ninth case of recurrent meningitis associated with C6 deficiency. Streptococcal meningitis had never been reported in such cases.