In November 1977, an enzyme-linked immunosorbent assay for detecting rotavirus antigen was introduced in the laboratory of a rural treatment centre in Bangladesh. During the next 40 days rotavirus without other pathogens was found in the stools of 216 (45%) of 480 children under age 5 years who visited the centre with a gastrointestinal illness. 188 (87%) of these children were treated with oral rehydration alone, using the solution currently recommended by the World Health Organisation, while 28 (13%) also required some intravenous rehydration; there were no deaths. Oral rehydration treatment was judged successful in 205 (95%) of the rotavirus patients and was not associated with any serious side effects. Oral rehydration treatment, with this solution, has been used extensively and successfully in the treatment of enterotoxin-mediated diarrhoea and can also safely be used for treating rotavirus diarrhoea in infants and young children.