AbstractThis paper considers the moral status of bystanders affected by medical research trials. Recent proposals advocate a very low threshold of permissible risk imposition upon bystanders that is insensitive to the prospective benefits of the trial, in part because we typically lack bystanders' consent. I argue that the correct threshold of permissible risk will be sensitive to the prospective gains of the trial. I further argue that one does not always need a person's consent to expose her to significant risks of even serious harm for the sake of others. That we typically need the consent of participants is explained by the fact that trials risk harmfully using participants, which is very hard to justify without consent. Bystanders, in contrast, are harmed as a side‐effect, which is easier to justify. I then consider whether the degree of risk that a trial may impose on a bystander is sensitive to whether she is a prospective beneficiary of that trial.