Vietnam's HIV epidemic has been driven by injection drug use, with HIV prevalence among injection drug users (IDUs) of ~30%. Most IDUs are sexually active and may infect their female sexual partners (SPs). Male dominance in sexual decisions is deeply embedded in Vietnamese culture. There have been few HIV prevention interventions for SPs, who represent an important potential bridging population in the epidemic. We report findings from a baseline survey of SPs conducted in 2008 in Hanoi, Vietnam, where peer-based HIV prevention interventions targeting this population are now being implemented. The survey revealed HIV prevalence of 14% among SPs in Hanoi and only 27% reported condom use with their primary male partners half the time or more. About 69% of SPs were in serodiscordant or unknown HIV status relationships but condom use was not more frequent in these relationships than in concordant partnerships. Many SPs feared angry or violent responses if they requested condom use, problems that were even more likely in serodiscordant/unknown status relationships. SPs also reported limited prior access to HIV prevention services. Many SPs in Vietnam are at high risk for HIV and in need of HIV prevention interventions. However, to date, this population has been seriously underserved. Our interventions are in progress and results will be reported subsequently.