Although rotavirus has been recognized as the most common etiologic agent of gastroenteritis in infants requiring hospitalization, there are several important gaps in the understanding of rotavirus infection. Obstacles to such an understanding have included difficulties in cultivating the virus from human stools, the lack of a simple animal model to examine the immune response, and differences in the epidemiology of the infection in developed vs. developing countries. There is a strong need for community-based longitudinal studies of rotavirus infections over a period of time, especially in developing countries. This article summarizes current knowledge of the rotavirus structure, genetic variations, antigenic components, epidemiologic features, clinical aspects and treatment, and prevention of rotavirus diarrhea. The typical clinical picture of rotavirus gastroenteritis is indistinguishable from diarrheas of other etiologies; however, dehydration occurs more frequently in children with rotavirus infection. The enzyme-linked immunosorbent assay is generally considered the most efficient and simple method of identifying rotavirus in the stool. Several approaches to rotavirus vaccines are currently being tested, and among the vaccine candidates are strains of rotavirus naturally attenuated for humans, cold-adapted strains, and laboratory-derived reassortants. Also under exploration is the potential of genetic engineering techniques to achieve in vitro production of rotavirus antigen.