This study investigated how many stable partners of drug users (DUs) had a history of drug use or were current DUs. Of 589 DUs interviewed, 41% reported that they had a partner with current or previous experience of drug addiction. A strong gender difference emerged: 77% of female DUs reported a stable relationship with partners with a history of addiction, versus only 30% for male DUs. Partners with a history of drug dependence are more likely to be: male, older, with a lower educational level and a lower rate of stable employment than partners without a history of drug addiction. Logistic regression analysis indicated that the characteristics of heroin users who have current partners with histories of drug use include: female gender, older age, living with a partner, lengthy duration of the relationship and HIV positive status. Fewer subjects are married if the partner has a history of addiction, and there is an association between lengthy drug use and partner without drug addiction history. The high percentage (59%) of subjects who were in stable relationships with partners without histories of heroin addiction and the relatively long duration of these relationships, raises the issue of possible transmission of blood-borne viruses from the DUs to their sexual partners. The study does suggest the need for consideration of sexual partnerships and gender differences in providing drug abuse treatment for heroin users.