Recruitment processes for clinical trials are governed by guidelines and regulatory systems intended to ensure participation is informed and voluntary. Although the guidelines and systems provide some protection to potential participants, current recruitment processes often result in limited understanding and experiences of inadequate decision support. Many trials also have high drop-out rates among participants, which are ethically troubling because they can be indicative of poor experiences and they limit the usefulness of the knowledge the trials were designed to generate. Drawing on recent social-psychological and philosophical-ethical research on trial recruitment and patient participation in treatment decision-making, this paper identifies possibilities for improving communicative support for both initial decisions and ongoing participation in clinical trials. It highlights the potential of a shift in thinking about 'voluntariness', underpinned by relational understandings of autonomy, to encourage more nuanced judgements about the ethics of communication between trial staff and (potential) participants. The paper suggests that the idea of responsively enabling people to consider invitations or requests to participate in particular trials could serve as a general guide to communication. This might help ensure decisions about trial participation are meaningfully informed and voluntary, and that relationships between trial staff and participants contribute to positive experiences of trial participation and ultimately to the generation of the robust knowledge. Copyright Article author (or their employer) 2012.