Abstract: Objective To analyze the pathogens of hand,foot,and mouth disease(HFMD)and the molecular epidemiology of enterovirus 71(EV71)in Tianjin. Methods A total of 2 377 clinical specimens from HFMD patients in Tianjin,2008-2010,were tested by real-time reverse transcription-PCR(RT-PCR).EV71 strains were isolated from some EV71-positive specimens.VP1 genes of the EV71 isolates were amplified by RT-PCR and sequenced.Phylogenetic tree was constructed after homology analysis of VP1 genes. Results Total positive rate of pan-enteroviruses was 70.72% (1 681/2 377)in the HFMD cases.Among the cases,48.30% were positive for EV71,37.36% for CV-A16,and 14.34% for other enterovirus cases.The thirty-one EV71 isolates had the highest homology(95.7%-99.2%)with the reference strain of C4a cluster of the C4 subgenotype.Phylogenetic analysis of entire VP1 gene of the EV71 isolates showed that they belong to C4a cluster of the C4 subgenotype. Conclusion EV71 was the principal pathogen of HFMD in Tianjin,2008-2010.The epidemic strains were C4a viruses of the C4 subgenotype.