It has been over 10 years since we first showed an association  between classical hemolytic uremic syndrome (hemolytic anemia, thrombocytopenia, and uremia, following a diarrheal prodome) and certain E. coli  capable of producing a toxin, initially called verotoxin (VT) because of its cytopathic effect on Vero cells  and later Shiga-like toxin (SLT) because of the toxin's close biological and structural similarity to Shiga toxin. Although we initially reported that 75% of children with idiopathic hemolytic uremic syndrome (HUS)  had evidence of a verotoxin-producing E. coli (VTEC) , a later study showed that over a seven year period (1980-86), of 86 children seen with HUS, 91% had a classical presentation and 88% of these had evidence of a VTEC infection . This paper traces the path of the incriminating organisms (VTEC) from the time of ingestion, up to and including internalization of the toxin into a target cell; in vitro experiments demonstrating the effect of toxin on endothelial cells are included. It is hoped that we might gain a clearer insight into factors that might predispose an individual to contracting HUS. Once a better understanding of the pathogenesis of VTEC associated HUS is known, areas for therapeutic intervention might be realized.