Abstract: Objective To explore the prevalence and the genetic diversity of norovirus among diarrheic children in Tianjin.Methods A total of 310 fecal specimens were collected during the period of October through December,2008 from infants and children with viral diarrhea hospitalized at the Tianjin Children's Hospital.Norovirus was detected with reverse transcription-polymerase chain reaction(RT-PCR) of the capsid gene and confirmed by sequencing,then followed by phylogenetic analysis.Results Among 310 specimens,37(11.94%) were positive for norovirus by RT-PCR.By comparative analysis with Genebank Blast and phylogenetic analysis of 23 norovirus sequences,22 norovirus cases(95.65%) were GII-4/2006b and 1 norovirus case(4.35%) was GII-3.Children aged less than 1 year were the most susceptible population to nornvirus infection which were usually found in November.Conclusion Norovirus is the major causal agents of viral diarrhea among hospitalized children with gastroenteritis in Tianjin and norovirus GII-4/2006b is a predominant genotype in 2008.