Objective To investigate the status and influencing factors of previous and new human immunodeficiency virus( HIV) infection among men who have sex with men( MSM) in Xi'an city. Methods A total of 2 444 MSMwere recruited with snow-ball or respondent-driven sampling in Xi'an city; a face-to-face questionnaire survey and 3-5 ml venous blood collection for the determination of HIV immunoglobulin G( IgG) with HIV-1 subtypes B,E and D( BED)capture enzyme immunoassay( BED-CEIA) were conducted among the MSMbetween...