In this study based on 2 personal cases and 23 cases from the literature the main clinical and therapeutic features of meningitis caused by Bacteroides fragilis are reviewed. The disease occurs in either very young or elderly people, with contributing factors in 54% of the cases. Clinically, the infectious syndrome is associated with meningoencephalitis and sometimes motor disorders. Although septicaemia is present in 80% of the cases, the patient's general condition is moderately affected. Blood leucocyte counts are definitely increased and CSF disturbances are those common to all types of bacterial meningitis. The initial focus of infection can be determined in 60% of the cases. The mortality rate is higher in adults than in children. Neurological complications are frequent. Nitro-imidazole derivatives, which are active against Bacteroides fragilis and reach high CSF concentrations, constitute the treatment of choice.