Objective: To examine whether needle exchange program (NEP) use by injecting drug users (IDUs) affects injection risk behaviors over time. : Between 1997 and 2000, 901 IDUs in Chicago were recruited for a cohort study from a multisite NEP and an area with no NEP. Participants were interviewed and tested for HIV at baseline and 3 annual follow-ups. Non-NEP users received HIV prevention services consistent with the Indigenous Leader Outreach Model. Random-effect logistic models were used to

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... e 5 injectionrelated risk behaviors between NEP users and nonusers. Methods Results: The 30-day prevalence of receptive needle sharing decreased from 27.6% at baseline to 10.0% at visit 4 in NEP users and from 47.1% to 20.0% in nonusers. Similar patterns were observed for lending used needles, and NEP users were less likely to reuse their own needles. In multivariate analyses, NEP use was significantly associated with reduced odds of greater than 60% for receptive needle sharing, 45% for lending used needles, and 30% for sharing other injection paraphernalia as well as approximately a 2-fold increase in the odds of always bleaching used needles. Conclusions: NEP use facilitates long-term reductions in injection risk practices, and the reductions are in addition to the effects of a behavioral intervention alone.