In a prospective study of rotavirus (RV) diarrhoea in Indian (Asian) infants in South Africa, it was found that in common with findings elsewhere in the world, vomiting and dehydration are prominent features of this disease. The dehydration was usually isotonic, though both hypo- and hypernatraemia did occur. Hypokalaemia was found to be much less common in RV than in non-RV diarrhoea. Unlike findings elsewhere, no definite 'rotavirus syndrome' associated with pyrexia and respiratory symptoms could be identified in RV diarrhoea as these occurred with equal frequency in non-RV patients. The mean total duration of RV diarrhoea (i.e. before admission plus during the hospital stay) was 5 days. The RV patients took significantly longer to recover from their diarrhoea than the non-RV ones, and mixed RV-bacterial infections prolonged the illness even more. Breast-feeding was associated with milder disease. Less than 2% of both RV and non-RV cases developed persistent diarrhoea of longer than 14 days' duration and this was most frequent in patients under 6 months of age with poor nutritional status.