Between September and November 1988, six children (aged 4-17 months) from a parish in Upper Bavaria fell ill with a haemolytic-uraemic syndrome. The illness had been preceded by a gastroenteritis with at times haemorrhagic stools. All patients needed peritoneal dialysis for acute renal failure. A 12-month-old girl was left with statomotoric developmental impairment due to cerebral involvement, but the other five children were cured. In the first four children to be admitted stool examinations for the common enteritis-causing microorganisms had been negative. But in the following two, specific gene probes demonstrated enterohaemorrhagic E. coli O157: H- with formation of verotoxin 2 (Shiga-like toxin II). This group of microorganisms must be taken into account in the diagnosis of haemorrhagic enterocolitis, because they can cause severe complications.