In two separate studies, faecal samples were collected from children with acute gastroenteritis; the samples were tested both by electron microscopy and immunoelectroosmophoresis with a view to detect reo-like virus. In 94 per cent and 100 per cent of samples positive by electron microscopy in the first and second material, respectively, a precipitin line was found after electrophoresis, using a guinea pig antiserum against a purified bovine virus. No false positives were detected by this method.