Diarrhoeal disease caused by enteric bacterial pathogens has become less prevalent in industrialized countries, but remains an important cause of morbidity and mortality in developing countries. Although better management of acute diarrhoeal episodes has led to more favourable outcomes, persistent diarrhoea remains a problem for which risk factors are being recognized and associated bacterial pathogens identified. Unusual or intractable diarrhoea should alert health workers to the possibility of impaired immune function, which is associated with a range of enteric pathogens and opportunistic infections. Improved microbiological methods have resulted in more frequent detection of pathogens in association with diarrhoea, as well as greater understanding of pathogenesis. Clinical features of diarrhoeal disease and mechanisms involved in pathogenesis are discussed in relation to specific bacterial enteric pathogens.