Acute gastroenteritis (AG), which may be caused by bacteria, parasites and enteropathogenic viruses, including rotaviruses, astroviruses, adenoviruses and caliciviruses, is an important health problem. The frequency of rotavirus as a cause of sporadic cases of AG ranges between 17.3% and 37.4%. Although it has been suggested that common exposure is not an important factor in the diffusion of rotavirus, it is difficult to associate apparently sporadic cases, meaning that there are probably outbreaks that go undetected. Astroviruses cause GA with a frequency ranging between 2 and 26%: outbreaks have been described in schools and kindergartens, but also in adults and the elderly. The frequency of identification of adenoviruses 40 and 41 as causes of sporadic AG in non-immunosuppressed children ranges between 0.7% and 31.5%, although there is probably underreporting because the sensitivity of conventional techniques is low. Caliciviruses are separated phylogenetically into two genera: Norovirus and sapovirus. Norovirus is frequently associated with food- and water-borne outbreaks of AG. It is estimated that 40% of cases of AG due to norovirus are foodborne. In Sweden and some regions of the United States, norovirus is the first cause of outbreaks of foodborne diseases. Sapovirus outbreaks due to person-to-person and foodborne transmission affecting both children and adults have recently been reported in countries such as Canada and Japan.