Central nervous system manifestations typically occur with Shigella gastroenteritis and also in enteric Salmonella and Campylobacter infections. To date no association between enteroinvasive Escherichia coli infection and neurologic symptoms has been described. Two children with diarrhea caused by E. coli 0144:NM had otherwise unexplained encephalopathy manifested by profound stupor in one child and by obtundation and meningismus in the other one. These cases of infection occurred in northern Israel during a period of an unusually high rate of enteric infection caused by this organism. None of the microbiologic properties studied were uniquely attributable to the encephalopathic cases. The two encephalopathic as well as all eight nonencephalopathic isolates studied possessed the 140-MDa invasive plasmid. All 10 isolates examined produced small amounts of cytotoxin by the HeLa cell assay, all were nonmotile, and all had identical antibiograms. Eight of 10 of the isolates had identical plasmid profiles, while 2 isolates (from nonencephalopathic patients) had slightly different plasmid profiles. This is the first report of encephalopathy associated with enteroinvasive E. coli.