AIMS: To determine the HIV-1 seroprevalence, risk behaviors and demographic characteristics associated with HIV-1 infection among injection drug users (IDU) in rural Guangxi, China. DESIGN AND SETTING: Between July and November 2002, 702 IDU were screened for HIV-1 antibody through community outreach in rural Guangxi, China for enrollment in an HIV sero-incidence study. PARTICIPANTS: A total of 702 active high-risk IDU were screened. High-risk injection was defined as anyone who reported injecting drugs at least three times per week in the last month or injected drugs with shared equipment on at least three occasions in the last 3 months. MEASUREMENTS: HIV-1 antibody testing with confirmation by Western blot was performed on all subjects. Demographic and risk assessment survey data were collected at screening from everyone whose baseline HIV antibody status was known. FINDINGS: HIV-1 antibody prevalence among 702 IDU at baseline was 25% with a median age of 26.7 years (18.2-43.2). Based on a multivariate logistic regression model using risk factors identified in univariate analyses, the following risk factors were associated significantly with an increase in risk for HIV seropositivity: age > 26 years (OR 1.50; 95% CI 1.04, 2.17), sharing of rinse water (OR = 1.24; 95% CI 1.09, 1.40), not having sex in the last 6 months (OR = 1.62; 95% CI 1.08, 2.43). CONCLUSIONS: HIV infection among IDU in Guangxi, one of China's major HIV epidemic regions, is high and the infection occurs predominantly among older IDU males who share rinse water.