Acinetobacter baumannii is an important pathogen which causes severe nosocomial infections such as meningitis. Multidrug resistance is a growing problem throughout the world. In this report a case of multidrug resistant A.baumannii meningitis, treated with high dose of ampicillin-sulbactam (SAM) was presented. Rhinorrhea and confusion developed on the postoperative seventh day in a 67 years old male patient operated for macroadenoma of the hyphophysis gland. Since the cerebrospinal fluid (CSF) findings indicated a central nervous system infection, nosocomial meningitis was diagnosed and intravenous ceftazidime and vancomycin have started. Blood and CSF cultures of the patient revealed no growth and his general condition has improved. However, fever and confusion emerged again on the 21st day of therapy and the repeat CSF sample revealed increased pressure, purulent appearance, 510/mm3 leukocytes (90% PMNL), 58 mg/dl glucose (simultaneous blood glucose was 144 mg/dl) and 49 mg/dl protein. Direct microscopic examination of CSF revealed gram-negative coccobacilli and A.baumannii was identified in the culture. The isolate was resistant to piperacillin-tazobactam, third generation cephalosporins, aztreonam, ciprofloxacin, carbapenems and aminoglycosides, susceptible to sulbactam ampicillin and colistin. Ampicillin (12 gr) and sulbactam (6 gr) treatment was initiated and at the 72nd hour of the therapy the temperature and conciousness level of the patient returned to normal. Control CSF sample obtained on the 14th day of treatment revealed no leukocytes and no bacterial growth. The treatment was continued for 21 days and the patient recovered without any sequela. Since colistin which is one of the alternative antimicrobial treatment choices for resistant Acinetobacter infections, is not found in Turkey, sulbactam-ampicillin might be an effective and safe choice for the treatment of multi-resistant A. baumannii meningitis if the isolate was proven to be susceptible by antibiotic susceptibility tests.