An analysis is presented of the duration of hospitalization of the patients with acute bacterial (purulent) meningitis which occurred at Boston City Hospital during 12 selected years between 1935 and 1972. Considerable differences in the length of stay in the hospital were noted depending on the bacterial etiology, whether the infection was present on admission or acquired within the hospital, and, of course, whether the patient survived or died. Most of the deaths occurred within the first few days after admission or after the diagnosis was first established, but even among fatal cases, the survival time differed depending on the etiology and site of acquisition of the infection. During the years after effective antibiotics became available the hospital stay of patients who survived after admission for meningococcal, influenzal, or pneumococcal meningitis was shorter than before. The same has not been true for meningitis caused by other gram-positive cocci, gram-negative rods, or mixed infections, probably reflecting the relative ineffectiveness of antimicrobial therapy in such patients.