Injecting drug users made up a high percentage of HIV cases in China; partners of IDU are hence, at very high risk of HIV transmission. The goal of this study is to compare characteristics and prevalence of injecting drug use and sex-related risk behaviors among female IDU who were or were not having a regular sex partner (RSP) with concordant IDU status. Data were obtained from all female IDU respondents (n=1414) surveyed in the behavioral surveillance surveys as conducted during 2003 through 2006 in Sichuan and Yunnan, China. The findings from this research reveal that about half of the female IDU respondents belonged to the concordant group (50.4%). As compared to members of the discordant group, such concordant respondents were significantly more likely to have practiced different types of studied syringe sharing behaviors (adjusted odds ratios AOR=1.34-2.23, p<0.05), to have served as female sex workers in the last month (AOR=1.24, p<0.05), or to have used some particular types of HIV-related prevention services (AOR=1.36-1.60, p<0.05) but were less likely to be always using new needles for drug injection in the last month (AOR=0.54, p<0.05) or to have used a condom in the last episode of sex with their RSP (AOR=0.64, p<0.01). The findings suggest that concordant IDU status is very common among RSP of IDU. The risk for HIV transmission between concordant RSP seems to be very high and the prevention services seem unable to alleviate the risk. Specific programs targeting concordant IDU couples are greatly warranted.