The paper contains a general discussion of the epidemiological and immunological features of meningitis. Data are presented on carrier rates extending over a period of somewhat more than a year. Type I rates made up only about 15% of the total, and remained remarkably constant over most of the time but rose sharply during the past winter slightly in advance of the increase which occurred in cases of the disease. An expt. is described in which small doses of sulfadiazine orally cleared up a large group of carriers.