AIMS:To examine injecting drug user (IDU) motivations as research participants. DESIGN:Convenience sampling facilitated by recruitment notices distributed through needle and syringe programmes (NSPs), and snowballing within peer networks. SETTING:NSPs in six suburbs throughout the Melbourne metropolitan area. PARTICIPANTS:One hundred and fifty-four current IDUs. The mean age was 28 years, 62% were male, and 80% nominated heroin as preferred drug. MEASUREMENTS:Interviewer-administered survey including questions about socio-demographics, drug use and main reasons for participating in research. FINDINGS:IDU research participation reasons were consistent with motivational themes such as economic gain (46%), expression of citizenship (38%), altruism (19%), personal satisfaction (17%), drug user activism (16%) and seeking information or assistance (5%). Most respondents (58%) cited reasons where the primary beneficiaries of participation were other individuals or groups (citizenship, altruism, drug user activism) or both self and others. CONCLUSIONS:IDU motivations for research involvement appear to be multi-dimensional, rarely motivated by economic gain alone, and not necessarily defined by direct benefits or gains to themselves. These findings are relevant to the question of IDU research payment ethics.