Escherichia coli O157:H7, although recognised 15 years ago, has only become a significant pathogen since 1982 when two outbreaks of haemorrhagic colitis due to this organism were described in the USA. Since then, numerous such outbreaks have been reported. Recent experience with a patient presenting with E. coli O157:H7-induced haemorrhagic colitis is described. The main features, pathological findings and investigations are described and the principles of management outlined.