ENGLISH :
Objective: To determine if HIV treatment-related attitudes are associated with unprotected sex and needle sharing among HIV-seropositive and -seronegative injecting drug users (IDU) in Baltimore, Maryland. Design and methods: IDU participating in a cohort study seen between December 2000 and July 2001 completed an interviewer-administered questionnaire on attitudes toward HIV treatment and risk behaviors (593 HIV-seronegative, 338 HIV-seropositive), including: perceived HIV transmissibility through unprotected sex and needle sharing, and safer sex and injection fatigue. Logistic regression was used to examine the role of attitudinal factors on needle sharing and unsafe sex. Results: Almost two-thirds of sexually active participants engaged in unprotected sex and approximately half of those injecting drugs shared needles. Among HIV-seropositive IDU, perception of reduced HIV transmissibility through unprotected sex was significantly associated with unprotected sex [adjusted odds ratio (AOR), 3.33; 95% confidence interval (CI), 1.05-10.55). Safer injection fatigue was independently associated with needle sharing among HIV-seropositive IDU (AOR, 6.55; 95% CI, 1.69-25.39). Among HIV-seronegative IDU, safer sex fatigue and safer injection fatigue were independently associated with unprotected sex (AOR, 3.12; 95% CI, 1.17-8.35) and needle sharing (AOR, 5.15; 95% CI, 2.33-11,37), respectively. Conclusion: Among HIV-seropositive IDU, perceiving that HIV treatments reduce HIV transmission was significantly associated with unprotected sex. Risk reduction fatigue was strongly associated with unsafe sexual and injection behaviors among HIV-seronegative individuals. HIV prevention interventions must consider the unintended impact of HIV treatments on attitudes and risk behaviors among IDU. (Author' s abstract)