The medical records of 25 patients with nosocomial meningitis due to Acinetobacter baumannii were retrospectively reviewed. Most cases occurred in the neurosurgical intensive care unit over a 5-year period, with an increased rate during summer. The majority of infections were associated with indwelling ventriculostomy tubes or CSF fistulae in patients receiving antimicrobial therapy. Repeated environmental cultures failed to reveal a source of the microorganism, and control measures had no apparent effect on the outbreak. However, no further cases appeared following a sharply reduced total intake of antibiotics in the neurosurgical department. Forty-one cases of acinetobacter meningitis, secondary to invasive procedures, were found in the English-language literature and were compared with the cases presented. To our knowledge, our series is the largest of acinetobacter meningitis reported hitherto. Although not one of the most common pathogens in hospitals, Acinetobacter constitutes an increasing threat for patients, especially those receiving antimicrobial therapy in intensive care units who are being maintained by various life-support systems.