This study assessed injection-related HIV risk behavioral changes among opioid users 6 months after enrollment in low-threshold (harm reduction based) metha-done maintenance treatment (MMT) programs within needle exchange services in Kingston and Toronto, Ontario, Canada. Changes were assessed for all participants (whole cohort), participants who continued to use illicit drugs by any route (drug-using subcohort); and those who continued to inject drugs (injecting subcohort). In this prospective observational cohort study, an interviewer-administered questionnaire examining injection-related HIV risk behaviors was administered to 183 study participants at entry to treatment and 6 months later. Changes in risk behaviors were analyzed using conditional logistic regression which took into account the paired nature of the data. We found that the proportion of participants injecting drugs, sharing needles, sharing drug equipment, indirectly sharing and using shooting galleries declined with follow-up for the whole cohort. Within the drug-using subcohort, there was a decrease in the proportion of individuals who injected drugs, while within the injecting subcohort the sharing of injection equipment and the use of shooting galleries declined. Our findings suggest that low-threshold MMT programs can reduce the risk of HIV without the enforcement of abstinence-based policies.