Enterobacteriaceae are not a frequent cause of meningitis in adults and are seen mainly in neurosurgical patients and on occasion in elderly and debilitated patients. Consequently, most series studied have been small and selected. In order to obtain a clearer clinical picture, we reviewed 20 consecutive cases of Enterobacteriaceae meningitis admitted to the Department of Infectious Diseases, Rigshospitalet, Copenhagen, during the years 1977-97. They comprised 1.5% of all cases of acute bacterial meningitis admitted to the department. All of the patients were either elderly and/or had 1 or more underlying diseases and predisposing factors. The clinical presentation and cerebrospinal fluid findings were not different from that of acute bacterial meningitis in general. The mortality rate was 40% and correlated with simultaneous bacteraemia. Complications were seen in a further 30% of patients and 25% survived with different sequelae. These high rates may, at least in part, be due to the advanced age and debilitated state of the patients studied. Escherichia coli was the most frequent of the Enterobacteriaceae.