Introduction: People who inject drugs (PWID) are stigmatized by society. Over time people may begin to internalize the stigma about their group. This research examines how implicit and explicit internalized stigma among PWID relates to health care and treatment access, psychosocial functioning, and engagement in risky behaviors.Methods: PWID were recruited from a needle and syringe program (NSP) located in Sydney, Australia. Participants completed a survey examining explicit and implicit internalized stigma, risky behaviors (e.g., sharing injecting equipment, unprotected sex), health care and treatment access (e.g., comfort attending NSPs), and psychosocial functioning (e.g., mental health). Detailed demographic variables were also collected.Results: A total of 115 clients completed the measures. To the degree that participants had internalized the stigma about their group (measured explicitly), they felt less comfortable attending NSPs, had greater severity of dependence, and experienced more depressive symptoms. The implicit measure of internalized stigma was related to treatment engagement and needle sharing, although the direction of these effects was unexpected.Conclusions: This research highlights the importance of ongoing research into the implications of internalized stigma for PWID. Assessing both explicit and implicit internalized stigma appears to be beneficial as these are related to different health and behavioral outcomes. [ABSTRACT FROM AUTHOR]