The prevalence and correlates of sexual risk behaviors among drug users in western China and the implications for HIV transmission in this population are described. A cross-sectional survey of male drug users was conducted in methadone maintenance therapy clinics and detoxification centers in three western provinces of China between September 2009 and December 2010. Participants in the study completed a questionnaire about demographics, HIV/AIDS knowledge, drug use history, sexual risk behaviors, and other psychosocial variables. Factors associated with HIV sexual risk behaviors were identified by multiple logistic regression analysis. Of 1,304 drug users surveyed, nearly 54% never used condoms during sexual intercourse with a spouse or cohabitant, and this behavior was associated with coming from Chongqing (OR=1.86, p<0.05), being aged 36 and older (OR=5.03, p<0.05), being married or cohabiting (OR=1.68, p<0.05), having first taken drugs at age 30 and above (OR=1.80, p<0.05), and having received AIDS advice or detection from authorities in the past year (OR=1.95, p<0.05). Twenty-six percent had had sex with casual sexual partners in the past year, and this behavior was associated with being married or cohabiting (OR=0.30, p<0.05), first taking drugs at age 31 and above (OR=0.42, p<0.05), and receiving AIDS advice or HIV detection from authorities in the past year (OR=0.70, p<0.05). About 34% never used a condom when having sex with casual sexual partners, and this behavior was associated with coming from Guangxi (OR=2.81, p<0.05) or Chongqing (OR=2.73, p<0.05). Almost 14% had had commercial sex in the past year, and this behavior was associated with coming from Guangxi (OR=6.26, p<0.05) or Chongqing (OR=5.44, p<0.05) and having exchanged needles or received clean needles from the Needle Exchange Centers in the past year (OR=2.76, p<0.05). Nearly 23% had never used condoms when having commercial sex, and this behavior was associated with having received free condoms from authorities in the past year (OR=0.26, p<0.05). Sexual risk behaviors among drug users in Guangxi, Chongqing, and Xinjiang are common. Additional intervention strategies are needed to control the spread of HIV in this population.