Microvascular endothelial damage underlies the pathological changes in haemorrhagic colitis and the haemolytic uraemic syndrome (HUS) caused by enterohaemorrhagic Escherichia coli (EHEC). Shiga toxins (Stxs) are presently the best characterised EHEC virulence factors that can cause the microvascular endothelium injury. Stxs are released by EHEC in the intestine, absorbed across the gut epithelium into the circulation, and transported to small vessel endothelial cells. Then, they presumably injure the host cell by inhibiting protein synthesis, stimulating prothrombotic messages, or inducing apoptosis. The net result is a multi-organ thrombotic process. Moreover, Stxs stimulate a variety of non-endothelial cells to produce and secrete inflammatory mediators (cytokines, chemokines, adhesion molecules) which could potentiate the effects of Stxs on endothelial cells. The association of HUS with Stx-negative E. coli strains stimulated intensive research on putative non-Stx virulence factors, which might also contribute to the pathogenesis of HUS and haemorrhagic colitis. Based on current data, cytolethal distending toxin, EHEC haemolysin, and subtilase cytotoxin might be such candidates.