Background: Previous research has shown that women drug users are exposed to increased risk for HIV infection and other sexually transmitted diseases within the context of their primary intimate relationships. However, the nature of such relationships and their effects on women's risk have received little attention. This study focused on intimate, heterosexual relationships among drug users in New York City to determine the impact of individual and relationship factors on women's risk.  Methods: Structured interviews were conducted with 353 low income, drug-using couples. Participants were African-American and Puerto Rican. Dyadic level relationship variables included dyadic adjustment, affect toward partner, and conflict resolution tactics, all measured by standard scales. Other variables included age, duration of relationship, living arrangements, and condom attitudes. Linear regression identified individual- and dyadic-level characteristics associated with behavioral outcomes: Results: Significant relationships (p value ≤.05) were between: 1) younger female age (t=-2.3), greater dyadic adjustment (t=3.9), negative condom use attitudes for women (t=3.9) and men (t=2.5), shorter relationship duration (t=-2.7) and frequency of unprotected sex; and 2) greater dyadic adjustment (t=2.3), negative condom attitudes for women (t=3.8) and men (t=2.0), any children under 18 living with female (t= -2.7) and a composite measure of women's sex & drug risk behaviors. Conclusions: Within primary intimate relationships, both individual and dyadic level factors are associated with women's risk for HIV. Most interventions targeted at women tend to focus on individual level variables; this study suggests that attention to relationship factors may also be crucial to reducing women's risk.