The use of social media as a recruitment tool for research with humans is increasing, and likely to continue to grow. Despite this, to date there has been no specific regulatory guidance and there has been little in the bioethics literature to guide investigators and institutional review boards faced with navigating the ethical issues such use raises. We begin to fill this gap by first defending a nonexceptionalist methodology for assessing social media recruitment; second, examining respect for privacy and investigator (...) transparency as key norms governing social media recruitment; and, finally, analyzing three relatively novel aspects of social media recruitment: the ethical significance of compliance with website “terms of use”; the ethics of recruiting from the online networks of research participants; and the ethical implications of online communication from and between participants. Two checklists aimed at guiding investigators and IRBs through the ethical issues are included as appendices. (shrink)