Background: Studies indicate that needle-exchange programmes (NEPs) can reduce the incidence of HIV infection; however, a positive impact of syringe-supply programmes has not been consistently demonstrated. The associations between high-risk injection behaviour and distance to and patterns of utilisation of syringe-supply programmes in injection drug users (IDUs) were investigated. Methods: Participants in a cohort of IDUs (n = 456) residing in Montreal were interviewed between 2004 and 2006. Behavioural questionnaires were administered by trained interviewers, and venous blood samples were drawn and tested for HIV antibodies. The distance from regular IDU dwelling places to nearest NEP or pharmacy was calculated using a Geographic Information System. Logistic regression was used to assess relations with high-risk injection behaviour. Results: Associations between high-risk injection behaviour and distance to syringe-supply source were not linear. The odds of high-risk behaviour grew modestly as distance from the NEP site increased to 1600 m, followed by a flat trend to 3000 m, and thereafter decreased with distance beyond this point. The odds of high-risk behaviour dropped sharply for the relatively few IDUs residing 1 km or more from the nearest pharmacy but this measure was not strongly associated with the outcome. IDUs who exclusively acquired syringes at NEPs or pharmacies had less than half the odds of reporting highrisk injection behaviour than IDUs with inconsistent syringe-access patterns. Conclusions: The study confirms that Montreal NEPs were implemented where they are most needed. These results also suggest that sterile syringe acquisition patterns might influence high-risk injection behaviour.