Bacterial meningitidis of the adult remain frequent and serious affections in spite of therapeutic progress. The authors report results from a retrospective study of 502 cases over 5 years. Hospital prevalence was 12.1%. These infections occur during the dry season between November and April in 75% of the cases. An important peak was observed in March, that is to say 24.5%. Patients' average age was 34.7 years old with extremes ranging from 15 to 80. The isolated micro-organisms were: the pneumococcus (45.2%), the meningococcus (14.5%), salmonella (1.6%) and the Haemophilus influenzae (1.2%). Meningitidis decapitated by a preliminary antibiotherapy represented 37,5%. Seroprevalence of the HIV infection during this work was 55.1%. Patients suffering from pneumococcus meningitis were contaminated by the HIV in 51.7% of the cases. Those suffering from meningococcus infection were infected with HIV in 52.9% of the cases. Those presenting meningitidis to Haemophilus influenzae and salmonellas had contracted the HIV respectively in 83% and 87.5% of the cases. The average duration of hospitalization was 14.2% days. The average mortality rate was 31.7% for the pneumococcus, 30. 1% for the meningococcus one. 53.4% of the patients recovered.