Abstract: To investigate whether the combination infection with different HIV-1 subtypes existed in HIV-1 infected population in China,and to analyse their infection source.Methods HIV-1 env gene was amplified by nested-PCR from uncultured peripheral blood mononuclear cells(PBMCs)obtained from 3 HIV-1 sero positive individuals found in Shenzhen.The C2-V3 region (360bp)o f them was sequenced and analyzed.Results Of 3 HIV -1 infectors,2(sz1 and sz8)were infected with subtype Thai B (Bc)and E with 23.52% and 20.69% intersubtype gene divergence inside individual,one subtype Europe and America B and C with 28.44% intersubtype divergence.In comparison of Bcon,Ccon,Econ HIV-1 internatiional reference sequence with corresponding subtypes found in these 3 infectors,the divergence waw 5.07-7.26%,3.23% and 5.38-5.99%,respectively.The tetra-peptide in the crown of gp120 V3 loop found in sz46 who was a drug user and prostitute was GPGR characterized for Europe and A merica B subtypes,others were GPGQ characterized for Thai B and E.Phylogenetic tree analysis further shown that sz1-2,sz81,sz46-1 were tightly clustered with international Bcon,sz46-2 with Ccon,sz1-1 and sz8-2 with Econ,respectively.Conclusion These findings suggested that 3 individuals were infected with two different HIV-1 subtype probably result from multirisky behaviors.