The efficacy of chemoprophylaxis in the treatment of basilar skull fractures was studied in 129 patients over a 2-year period; antibiotics were found ineffective in preventing central nervous system infections, and in some cases may have proved harmful. It is suggested that a more rational approach to the treatment of basilar skull fractures includes close observation of the patient for early signs of meningitis, and if these should develop, treatment with antibiotics appropriate to the organism involved.