The clinical and laboratory features of 96 children aged 6 to 36 months with acute rotavirus diarrhoea were compared to findings on 63 children of the same age with acute non-rotavirus diarrhoea. Of the rotavirus-associated cases 80% occurred between January and June. In general, the diarrhoea was more severe in these patients than in the others, but no difference was seen in duration of symptoms. Clinical features characteristic of rotavirus-associated cases included: dehydration and acidosis upon admission, vomiting, fever, neutropenia and sugar in the stools (Clinitest greater than or equal to 0.5%). In contrast, no difference was seen in the occurrence of respiratory symptoms (53% in the rotavirus, 62% in the non-rotavirus group), or in the presence of mucus strands, occult blood or leucocytes in stools. A combination of the above criteria may be helpful in the presumptive diagnosis of rotavirus diarrhoea.