Enterohaemorrhagic Escherichia coli (EHEC) is the cause of haemorrhagic colitis which may be complicated by subsequent haemolytic uraemic syndrome (HUS), thrombotic-thrombocytopenic purpura (TTP), and neurologic disorders. The organisms produce at least three biochemically and immunologically distinct cytotoxins which are designated as Shiga-like (SLT) or verotoxins and which are identified by immunological methods, cell culture tests, or gene-probes. According to present knowledge infections are primarily caused by consumption of contaminated milk and meat products and secondarily during outbreaks by human-to-human transmission. In North America cattle is considered as the main reservoir whereas in Europe sufficient information is lacking. EHEC produce different amounts of SLT; high toxin producers were identified in strains belonging to E.coli O157:H7, O157:H-, 026:H11, 0111:H8 and 0111:H-. Sporadic cases and two outbreaks due to EHEC have been identified in the Federal Republic of Germany. The life-threatening complications of the the disease, unknown reservoirs and vehicles of transmission of the organisms in Europe, and sophisticated diagnostic laboratory methods represent a clinical and microbiological problem and a challenge to the public health service.