Over a period of 2 months, 35 of 69 (51%) cases of juvenile diarrhoea studied in eastern Malaysia were associated with rotavirus excretion; rotavirus associated diarrhoea occurred most commonly in the 6-24 month age group. Polyacrylamide gel electrophoresis (PAGE) of genome ribonucleic acid showed that only 4 rotavirus electropherotypes could be detected. Of those, 2 predominated and 2 were detected only once each; one of these may have been a reassortment of the two predominant electropherotypes. Analysis of the clinical features of patients excreting rotavirus subgroup 1 or 2, determined by PAGE, demonstrated that rotavirus subgroup 1 was associated with more hypotonic dehydration and need for intravenous therapy: lethargy was significantly more common among those excreting rotavirus subgroup 2.