In order to assess the clinical features, aetiology, treatment and outcome of post-neurosurgical and post-traumatic Gram-negative bacillary meningitis (GNBM) we performed a retrospective review of all adult patients admitted to the Department of Neurosurgery who had Gram-negative bacilli cultured from cerebrospinal fluid (CSF) following a neurosurgical procedure or traumatic head/spinal injury. During the 12 y of the review 33 patients had CSF isolates of Gram-negative bacilli that were thought to be significant. The median patient age was 47 y (range 22-77 y) and 21 (64%) were male. Klebsiella pneumoniae, Enterobacter cloacae and Escherichia coli were the most common isolates. Minimal inhibitory concentrations (MIC) measured for half the patients' isolates resulted in 5 regimen changes, including 2 patients with E. cloacae meningitis in whom cephalosporin susceptibility decreased during cephalosporin treatment. Our recommended initial treatment was intravenous ceftriaxone and amikacin, subsequently tailored by susceptibility results; approximately half the patients remained on the antibiotics they started and half were changed to an alternate regimen, most often a carbapenem. Five patients (15%) died, 1 dying after cure of his GNBM. There were no failures in those who received more than 12 d of appropriate treatment: treatment for at least 14 d after the last positive CSF culture guaranteed cure. Initial ceftriaxone and amikacin subsequently changing to susceptibility driven alternatives, often a carbapenem, resulted in cure of 85% of our patients with GNBM.