During a period of nearly thirty-five years the members of the Division of Acute Infections of the Central Nervous System of the New York City Health Department have been studying the effect of the various forms of therapy in bacterial meningitis. Before the newer chemicals became available the case fatality in pneumococcic meningitis was 100 per cent. The use of azosulfamide and sulfanilamide slightly improved the prognosis. The advent of the more potent sulfonamides marked a further advance in the treatment of this disease. In an unpublished series of 139 cases of pneumococcic meningitis treated with sulfapyridine, sulfadiazine, sulfathiazole or a combination of these (and specific serum when available) we obtained 49 recoveries. The recent introduction of penicillin led us to try the use of this drug in pneumococcic meningitis. MATERIAL This report is based on a series of 67 consecutive cases seen between Oct. 10, 1943 and May 1,