Abstract: Objective To investigate HIV and syphilis infections and influence factors among drug addicts under compulsory rehabilitation in Qingyuan city.Methods From 2007 to 2008,a cross-sectional study was conducted among drug addicts selected with cluster sampling from three compulsory addiction treatment centers in Qingyuan city.Questionnaire survey was conducted to collect information on demographics and characteristics of drug use and sexual behavior,and blood samples were collected for tests of HIV and syphilis an tibodies.Results Among 740 drug addicts investigated, the in fection rates of HIV and syphiliswere 4.59% and 12.57%, and the coinfection infection rate was 1.22%.The results of multivariate logistic regression analysis showed that drug injection and syphilis infection were risk factors for HIV infection.Drugusers fromrural and town, with more accumulated times of drug detoxification and commercial sexbehavior had a higher risk of syphilis in fection.Conclusion The in fection rates of HIV and syphilis in drug addicts under compulsory addiction are higher than those of in general people as well as the coinfection.Drug in jection and commercial sexbehaviors are main risk factors for infections of HIV and syphilis.