The participants were part of the National AIDS Demonstration Research project, sponsored by the National Institute on Drug Abuse, and focusing on two targeted groups: intravenous drug users not currently in treatment and their sexual partners. All had received no drug treatment in the last 30 days, had injected drugs in the last 6 months, and were involved in sexual activity in the last 6 months. Data were collected from 1987 to 1991 in 63 sites in the United States. Results revealed that women who trade sex for money, drugs, or both, are less likely than other women to use new needles on any consistent basis or to clean old needles. Compared to women who support themselves by other means, they are more likely to share needles with others. Three identifiable patterns of needle-using practices emerged: indiscriminate sharing, monogamous sharing with a sexual partner, and the exclusive use of new needles. Findings suggest that to reach those engaged in promiscuous sharing, needle-swapping programs must be particularly user friendly. Where needle-using behaviors are part of an intimate relationship, the spouse or sex partner must be involved if change is to take place. Finally, policymakers and practitioners should take advantage of the strengths and strategies of those who report that they consistently use sterile needles. Tables and 24 references (Author abstract modified)