The authors have used an anti-rotavirus immunserum fixed to the Staphylococcus aureus protein A to detect this virus in the stools. A study on animal faeces showed a very good agreement in results with ELISA technique. The study on human stools shows a good agreement with ELISA technique and identical results to this technique in comparison with electronical microscopy. The agglutination reaction appears as a quick, simple and specific technique to find out rotavirus in the stools.