Studies from Europe indicate that infections with enterohemorrhagic Escherichia coli (EHEC) non-O157:H7 strains are increasing in frequency as a cause of hemolytic-uremic syndrome (HUS). In 1997 a prospective study was performed in Germany and Austria to assess the distribution of EHEC serotypes, to characterize the clinical course and to examine environmental aspects. 95 children with a diagnosis of HUS were evaluated in Germany and Austria. Diarrhea, which was bloody in 67%, was reported in 97% of patients. Oligo-/anuria occurred in 76% of patients, of which 63% required dialysis. Two patients showed neurological sequelae at the 2-month follow-up, both of them were infected with non-O157:H7 serotypes. Case fatality in the acute stage was 3/95, in two of these patients EHEC was isolated. Stool and serum specimens were analyzed for the presence of EHEC and antibodies against O157 lipopolysaccharide (LPS). Serotype O157:H7 was identified in 36/58 (62%) isolates, 22 strains (38%) belonged to non-O157:H7. Combining stool culture with serology, EHEC infection was documented in 88% of patients, including three patients without diarrhea. Non-O157:H7 serotypes occurred in 77% of children up to 36 months of age and were the most prevalent serotype in children up to 12 months of age.