Human astroviruses (HAstV) are now recognised as important causes of acute gastroenteritis in young children world-wide. The development of improved and more reliable diagnostic methods such as enzyme immunoassays and molecular methods has led to an increase in our understanding of the characteristics of astroviruses and astrovirus infections. Astroviruses can be classified into genogroups, genotypes and serotypes depending on whether genetic or antigenic criteria are used. Epidemiological studies have shown that astrovirus infections are associated with sporadic infections of children in the community as well as focal outbreaks in settings such as hospital wards and day-care centres. Astrovirus outbreaks have also been noted among adults. Recent reports have shown that, in some settings, astrovirus is the second most common cause of diarrhoea in children, thus establishing the medical importance of HAstV. World-wide, HAstV-1 seems to be the predominant type with varied distribution of the other types. Continued studies of the epidemiology of astrovirus infection and the extent of genetic variability of clinical isolates, coupled with an increased understanding of immune responses to astrovirus infection, are needed to develop strategies for the control of disease caused by this enteric pathogen.