Infectious diarrhoea remains a major cause of morbidity and mortality worldwide. Viruses, bacteria and protozoa are responsible for most infections, which are most commonly transmitted by the faecal–oral route through water, food and person-to-person transmission. Clinical presentation of infectious diarrhoea conforms to three patterns: acute watery diarrhoea; bloody diarrhoea (dysentery); and persistent diarrhoea, which can include steatorrhoea. Diagnosis still rests heavily on stool microscopy and culture, although faecal antigen tests and molecular assays are increasingly used.