In a series of patients with meningitis cared for over a period of 14 1/2 years there were 55 in whom the causative organism was identified as a pneumococcus. The overall mortality rate was 25 %, but in patients over 40 years of age the mortality rate exceeded 50 %. Only 4 of the patients had a demonstrable infection in their lungs; 18 had otitis media, and this was the most common factor in meningeal involvement. In 22 patients no primary source of the pneumococcal infection could be found. The most common neurological complication was damage to the cranial nerves and resultant visual and auditory deterioration. Among five patients who had recurrent pneumococcal meningitis there were a 7 1/2-year-old boy who died during his 6th attack and a 39-year-old woman who entered the hospital with her 15th attack and recovered. The treatment in 52 cases was penicillin given parenterally. There was no evidence of advantages in intrathecal injection. The authors suggest that sulfadiazine be given orally as long as penicillin is continued.