<p> Escherichia coli is a normal inhabitant of the human gastrointestinal tract and can cause healthcare-associated infections. The organism is most frequently responsible for urinary tract infections and it is the bacterium most often implicated in the cause of diarrhoea in people travelling overseas. In recent years, a strain called E. coli O157 has gained notoriety for causing foodborne infection, which can have severe health consequences, especially in young children. This article describes the range of different infections caused by E. coli in healthcare settings and the community and discusses the characteristics of the different strains of the bacteria that explain variations in their pathogenicity.</p>