This project examined sexual behavior and STI prevalence among HIV-infected individuals in South China. Adult HIV-infected outpatients in Guangzhou, Guangdong Province, China completed a self-administered survey about behaviors and antiretroviral treatment. Participants were screened for syphilis, gonorrhea, and chlamydia. Univariate and multivariate relationships with any STI were calculated using logistic regression. 810 HIV-infected individuals participated and 3 refused. 52.5 % (n = 415) of individuals reported having sex in the past 3 months, among whom 26.4 % (n = 111) reported inconsistent condom use. 10.4 % (n = 84) of all individuals had at least one sexually transmitted infection (STI). HIV-infected individuals not on antiretroviral treatment had an increased STI risk (aOR 2.5, 95 % CI: 1.4-4.5, P = 0.002). Unsafe sex was markedly reduced among HIV-infected individuals on treatment, possibly a reflection of integrated ART initiation counseling. Improved STI services among HIVinfected individuals are urgently needed to deamplify sexual HIV transmission.