Eight cases of neonatal meningitis due to Enterobacter sakazakii (formerly known as yellow-pigmented Enterobacter cloacae) which occurred in The Netherlands during the last 6 years were investigated retrospectively. Two patients had necrotizing enterocolitis and meningitis simultaneously. Despite treatment (in most cases with ampicillin and gentamicin), the fatality rate was 75%. Strains were much more susceptible to some of the new beta-lactam antibiotics than to ampicillin. A mode of transmission other than passage through the birth canal was likely, at least for some patients. A cluster of four patient strains in one hospital had almost identical plasmid DNA profiles. However, two strains isolated from formula at the same hospital 2 days after the onset of one case had different profiles, as did the strains from patients in other hospitals.