Background: Little is known about the complex stepwise process of giving up intravenous (IV) drugs. However, HIV risk reduction programs directed towards IV drug users have been accused by some opponents to encourage users to continue. In order to better assess the relationships between risk reduction and abstinence, we studied factors associated with abstinence in HIV-infected patients using IV drugs at enrollment in the SEROCO cohort (1988-1994). Methods: 63 HIV-infected patients injecting IV drugs at enrollment were followed-up every 6 months with a clinical examination and a questionnaire concerning sexual and drugs practices since last consultation. Abstinence was defined as non injecting for at least 6 months. The 30 patients who became abstinent during a follow-up period of 3 years were compared to the 33 remaining. Results: Abstinence during follow-up was not related to age at inclusion, duration of IV drug use, gender or marital status. However, patients who became abstinent were more likely to have a professional activity at inclusion than the remaining (70% vs 42%, p = 0.03). Before knowledge of HIV infection, frequency of injections, needle sharing and use of condoms did not differ between the 2 groups. During follow-up, behavioural changes occurred in the two groups, but were more marked in those who lately became abstinent. These latter were more likely to always inject with new needles/syringes (57% vs 18%, p = 0.003), and to use condoms with HIV-negative partners or of unknown status (73% vs 39%, p = 0.06). Professional activity and systematic use of new needles/syringes remained independently associated with abstinence in multivariate analysis. Conclusion: In this cohort, abstinence appeared as a stepwise process in which risk reduction preceded abstinence. This confirms that risk reduction programs do not work against those messages aimed at stopping IV drug use. Since this analysis selected particular subjects, enrolled in a cohort of HIV-infected patients, results should be confirmed in other samples of IV drug users.