Gram-negative bacilli are common organisms in nosocomial meningitis in adults. Escherichia coli containing the K1 capsule is the leading cause of gram-negative meningitis in neonates. Nosocomial gram-negative bacterial meningitis is a complication of a variety of surgical procedures, such as craniotomy, placement of internal or external ventricular catheters, lumbar puncture, intrathecal infusions, or spinal anesthesia; head injury; or at times secondary to metastatic infection in patients with hospital-acquired bacteremia. Among healthcare workers meningitis may frequently be caused by gram-negative bacilli. The mortality and morbidity associated with gram-negative meningitis have remained significant despite advances in antimicrobial chemotherapy. Some patients lack many of the classic features of bacillary meningitis, especially the elderly, and pose a diagnostic challenge. Acinetobacter meningitis is becoming an increasingly common cause of meningitis in postneurosurgical patients. The exact pathogenesis of gram-negative meningitis is not completely understood. A meta-analysis suggests that prophylactic antibiotics administered before craniotomy reduce rates of postoperative meningitis by one half. Some older antibiotics like polymyxins have been found useful for the treatment of several intensive care unit-acquired infections including meningitis. Intraventricular and lumbar administration of antibiotics can lead to a quick CSF sterilization in postneurosurgical patients with meningitis and ventriculitis. In this updated summary, Dr R K Garg reviews the latest information on the clinical features, etiology, pathogenesis, treatment, and outcome of gram-negative bacillary meningitis.