The efficacy of cephalothin and cephaloridine in the treatment of bacterial meningitis was evaluated from a review of 106 cases reported in the literature. Fifty-nine percent of 34 patients treated with intravenous cephalothin responded suboptimally; those receiving daily doses of 12 g or more fared significantly better (P less than 0.025). In contrast, 74% of 72 patients treated with cephaloridine responded favorably; those who received concomitant intrathecal cephaloridine responded significantly better (P less than 0.005). These findings indicate that cephalosporin therapy for bacterial meningitis, without concomitant intrathecal medication, is unreliable and that this is probably due to inadequate penetration of the antibiotics into cerebrospinal fluid. In penicillin-allergic patients with pneumococcal, meningococcal, and hemophilus meningitis, chloramphenicol is the agent of choice. For staphylococcal meningitis, intravenous cephalothin at doses of 12 g/day with additional intrathecal cephaloridine at doses of 12.5 to 50 mg/day should be administered concomitantly.