Illicit drug users are frequently identified as a ‘vulnerable population’ requiring ‘special protection’ and ‘additional safeguards’ in research. However, without specific guidance on how to enact these special protections and safeguards, research ethics committee (REC) members sometimes fall back on untested assumptions about the ethics of illicit drug use research. In light of growing calls for ‘evidence-based research ethics’, this commentary examines three common assumptions amongst REC members about what constitutes ethical research with drug users, and whether such assumptions are (...) borne out by a growing body of empirical data. The assumptions that form the focus of this commentary are as follows: (i) drug users do not have the capacity to provide informed consent to research; (ii) it is ethically problematic to provide financial incentives to drug users to participate in research; and (iii) asking drug users about their experiences ‘re-traumatizes’ and ‘re-victimizes’ them. (shrink)