Since their discovery in the 1970s, the human rotaviruses have been recognized as the most important cause of acute infectious gastroenteritis among infants and children worldwide. Rotavirus has been found to infect almost all mammalian and avian species tested, and is primarily a disease of the young. In humans, rotavirus is the most frequent gastrointestinal pathogen in infants and children less than 2 years of age. In developing countries, the attack rate peaks at 6 months of age, whereas in developed areas of the world the virus is most commonly found among children 6-12 months of age. Rotavirus displays a marked seasonality in temperate climates, with the number of cases peaking in the colder winter months. In tropical climates, this seasonality is not as apparent, and infection may occur year round. Symptoms of rotavirus infection are non-specific and include vomiting and diarrhoea, occasionally accompanied by a low grade fever. Dehydration is more common with rotavirus infection than with most bacterial pathogens, and is the most common cause of death related to rotavirus infection. Treatment is non-specific and includes the use of oral rehydration therapy, especially in developing countries where malnutrition is common. Strategies for the prevention of rotavirus infection are dependent on advances in the understanding of the molecular biology of the rotavirus. The genetic structure of the virus has been extensively studied, and a number of the structural proteins have been identified. The neutralization antigens, located on VP4 and VP7, may be important in conferring immunity to rotavirus in vivo. Two animal-derived and several reassortant rotavirus vaccines are currently being evaluated in field studies, and a number of other candidate vaccines are being tested in vitro and in animal studies.