A retrospective chart review was performed to evaluate the effect that positive results of cerebrospinal fluid bacterial antigen tests had on the care of patients with presumed bacterial meningitis. Of 901 tests ordered, costing $26,000 per year, 29 showed positive results--and only four of these affected patient care. By using cerebrospinal fluid bacterial antigen testing only when another test does not identify an organism, or in an attempt to determine central nervous system infection late in therapy for presumed sepsis, one can greatly reduce costs with no detrimental effect on patients.