The clinical features and the outcomes of eight cases of nosocomial Acinetobacter baumannii meningitis treated with ampicillin/sulbactam are reported. All the patients had fever, neck stiffness or meningeal signs, and a low consciousness level, and in their cerebrospinal fluid (CSF), pleocytosis, a low glucose level, and an elevated protein level were noted. For all CSF isolates of A. baumannii, the MIC of ampicillin/sulbactam was < or = 8/4 microg/mL. The MICs of sulbactam by microdilution in two cases were 4 microg/mL. All isolates were resistant to cefotaxime, ceftriaxone, ceftazidime, ureidopenicillins, ciprofloxacin, and gentamicin. Seven isolates were resistant to imipenem. A. baumannii was isolated from other samples in seven episodes. All patients were treated with ampicillin/sulbactam (seven with 2 g/l g every 6 hours and one with 2 g/l g every 8 hours). Six patients were cured and two patients died of meningitis. There were no side effects with the ampicillin/sulbactam treatment. In conclusion, ampicillin/sulbactam may be effective as therapy for meningitis caused by A. baumanii resistant to imipenem and other beta-lactam drugs.