From September through November 1990, an outbreak of hemorrhagic colitis associated with Escherichia coli O 157: H 7, occurred in a kindergarten in Saitama, Japan. Some of the patients suffered from neurological symptoms such as stupor, deep coma and/or convulsions in the acute stage, and/or action tremors, nystagmus, incontinence, phrenic nerve palsy in the later stage. Serum complements decreased more in the patients with neurological symptoms than in the patients without them. The verotoxin elaborated by E. coli O 157: H 7 was considered to cause the neurological symptoms, on the basis of their clinical courses and laboratory findings, especially the cerebrospinal fluid findings.