OBJECTIVE: To study the clinical manifestations for norovirus gastroenteritis in infants and young children. METHODS: Stool specimens were collected from infants and children with acute diarrhea who visited the affiliated Children's Hospital to Capital Institute of Pediatrics from January 2002 to December 2006. Enzyme-linked immunosorbent assay (ELISA) was used to detect human norovirus antigen in stool specimens and polyacrylamide gel electrophoresis (PAGE) was performed to detect rotavirus genome. RESULTS: Out of the 318 specimens under testing, 79 showed positive for norovirus antigen, with a positive rate of 24.8% (79/318). Among those positive specimens, 48(48/79, 60.8%) were detected in October to December, suggesting the seasonal preference of the virus. Most of the positive specimens (91.2%) were from those under 2 years of age. Rotavirus genome were detected from 16 out of 79 norovirus positive specimens (16/79, 20.3%), indicating those patients were co-infected by these two viruses. There was significant difference found in the severity of fever but not in the frequencies of diarrhea between rotavirus and norovirus co-infection group and noroviral infection group. Fourteen out of 79 norovirus positive patients were admitted to hospitals under the diagnosis other than gastroenteritis but started to develop symptoms of diarrhea between 1 to 11 days after hospitalization. CONCLUSION: Norovirus seemed one of the most important pathogens for acute diarrhea among infants and young children and could cause nosocomial infectious gastroenteritis.