OBJECTIVE: To understand the etiology of human rotavirus infections in children with acute gastroenteritis in China. METHODS: The investigation covered 1968 feces infants and children with acute gastroenteritis in 19 provinces and cities in China. Feces samples collected from 1968 infants and children with diarrhea, 148 children, 135 newborns and 37 adults without diarrhea, 36 adults with diarrhea were examined by polyacrylamide gel electrophoresis (PAGE). 1493 feces samples were examined by ELISA; 388 feces samples from sick children and 57 feces samples from children and adults without diarrhea were examined by EM. Bacterial culture were analyzed in 645 feces samples. RESULTS: Human rotavirus RNA (HRV RNA) was detected in 804(40.9%) of 1968 feces samples examined. No virus was detected in the feces samples of children and adults without diarrhea. Rotavirus antigen was detected in 500 (33.5%) of the 1493 feces samples. According to the genome profile of PAGE, 801 (99.6%) of the 804 rotavirus RNA positive belonged to group A virus, and the other 3 (0.4%) belonged to group C virus. According to the different migration of 10 and 11 segments on PAGE, the RNA pattern of group A rotavirus could be subdivided into two patterns: long and short patterns. The 527 (66.8%) positive HRV RNA was in the long pattern, while the 267 (33.3%) positive were in the short pattern. Among the rest 6 appeared to be mixed types, and the examined one was uncertain. Four different genotypes of HRV RNA in long and short patterns were identified respectively. They were types 4232, 4222, 3232 and 3222. The eight electropherotype genomes of HRV RNA varied not only in different years or seasons but also with the ages of patients and regions where the patients live. CONCLUSION: Rotavirus infections are the major cause of diarrhea of infants and young children throughout China.