HIV among injection drug users (IDUs) has exceeded that of any other risk group. Most HIV transmission occurs in social relationships. The hypotheses are that females will share syringes more frequently than males; men will not be more likely to share syringes with their sex partners than women; and if women share drugs with male network members, they will be more likely to share syringes with them compared to male network members with whom they do not share drugs. The data used were collected as a part of the SHIELD (Self-Help in Eliminating Life-threatening Diseases) project, a network-oriented experimental pre- and post-test intervention. Participants were recruited through targeted outreach. Men and women were compared in terms of sociodemographic variables and social network profiles. Results indicated that there were gender differences in the relationships between injecting partners that were associated with syringe sharing. Comparisons of men’s and women’s egocentric networks portrayed differential social risks associated with syringe sharing. On average, women’s overall social and support networks were significantly larger than men’s. In comparing all members of men and women’s social networks, women had a larger percentage of sex partners and kin. Women reported daily contact with a greater percentage of their network. This could facilitate women sharing syringes more often than men with network members due to the nature of their relationships. Close to one-half of men’s and women’s social networks was comprised of active users. As hypothesized, women shared syringes with a significantly larger proportion of network members compared to men, women’s larger networks with more drug users exacerbated their HIV risk, and HIV-infected women in methadone treatment had a higher number of current drug users and IDUs in their social networks compared to HIV-negative women. An unexpected finding was that men’s sharing of syringes was more highly associated with the drug use patterns of their injecting partners compared to women’s. 5 tables, 47 references