Infection with small round structured viruses (SRSV) usually causes an acute, but short-lived, attack of gastroenteritis in which vomiting is a prominent feature. Most documented outbreaks have occurred in institutional and catering establishments and infected food handlers are often implicated. Reports of SRSV infection have risen substantially during the last decade partly due to an increase in the number of laboratories able to examine samples for this organism. Ascertainment is likely to remain low, however, until a sensitive, simple, reliable and economical method of detection becomes routinely available.