An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of the human reovirus-like agent of infantile gastroenteritis in human stools. The results of the assay can be read either with a simple colorimeter or the naked eye. Investigations with 143 samples from children with gastroenteritis and 75 samples from children with other illnesses showed that the ELISA was as sensitive as electron microscopy or radioimmunoassay for detection of this agent. In addition, the ELISA was simple to perform and, when read visually, did not require sophisticated technical equipment. These advantages make it suitable for field work.