A cross-sectional survey was conducted in 2007 among 504 drug users who were recruited mainly from detoxification centers in southwest China. About one-third (34.3%) of participants reported recent risky drug use behavior, which was defined as injecting drugs in the past 3 months, and more than one-fifth (21.6%) reported recent risky sexual behavior, or had multiple sexual partners in the past 30 days. Male sex (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.2-3.2) and more episodes of detoxification (OR, 3.7; 95% CI, 2.3-6.0) were associated with higher odds of risky drug use behavior, while unmarried status (OR, 1.7; 95% CI, 1.0-2.9), higher personal annual income (OR, 1.8; 95% CI, 1.1-2.8) and history of sexually transmitted infections (OR, 3.7; 95% CI, 2.1-6.6) were associated with higher odds of having risky sexual behavior. Subgroup analyses showed 15% participants who used drugs in the past 3 months also shared needles, and 77% participants who had multiple sexual partners in the past 30 days did not use condoms during sex with non-primary sexual partners. The study findings are useful for developing HIV risk reduction intervention programs among drug users.