Recruitment challenges in clinical research are widespread, particularly for traditionally under-represented groups. Referral relationships—in which research partners and clinical partners agree to collaborate on selected research studies or programmes, with the expectation that the clinical partners refer appropriate patients as potential participants—may help alleviate these challenges. Referral relationships allow research partners access to expanded and more diverse pools of participants by increasing the engagement of medical providers, leveraging providers’ connections with patients and providing structural support for study participation. Clinical partners (...) can also benefit from the resources offered by research involvement, and patients may benefit from improved access to studies. Yet despite their potential, referral relationships can raise ethical concerns. Here, we discuss ethical considerations for referral relationships in clinical research to address these concerns. When establishing relationships, fair participant selection should guide the sites and studies involved. When defining the terms of a relationship, partners should build trust and respect, collaborating so that health centres or hospitals and communities benefit from their research involvement with the mitigation of associated burdens. When implemented, referral relationships should continue to honour fair participant selection, reduce misunderstanding or miscommunication about research and protect patients’ privacy and confidentiality. Overall, when conducted ethically, referral relationships can help address study recruitment challenges and promote fair access to research opportunities. (shrink)