ELISA and negative contrast EM have used for the detection of rotavirus in one hundred stools from children, less than two years old, hospitalized for acute gastro-enteritis during the winter 1977-78. Samples obtained from the same children some months after hospitalization were also tested. A good correlation was found between the results given by EM and ELISA, but the later technique turned out to be more sensitive (12% more positive using ELISA). A rotavirus infection could be demonstrated in 73% of the patients. In the stools of 3 children we found a second virus in association with the rotavirus, and in two cases a pathogenic bacterium. When a second serum specimen was available from children previously infected by rotavirus it was always possible to detect a significant increase in CF antibodies. Several months after hospitalization a 2nd survey indicated that the rotavirus was no longer present but calicivirus, echovirus, coxsackievirus and adenovirus could be detected in those asymptomatic children.