This thesis is a contribution to the ethical justification for clinical research with children. A research subject’s participation in a trial is usually justified, in part, by informed consent. Informed consent helps to uphold the moral principle of respect for persons. But children’s limited ability to make informed choices gives rise to a problem. It is unclear what, if anything, justifies their participation in research. Some research ethicists propose to resolve this problem by appealing to social utility, proxy consent, arguments (...) explaining why it is permissible to expose children to some harm, and an argument concerning the appropriate balance between research harms and benefits. I argue that each of these is a necessary part of the justification for research with children, but that the argument concerning harms and benefits is under-developed. It relies on the concept of minimal risk, but minimal risk is inadequately justified. I propose an interpretation of minimal risk. I defend the idea that minimal risk should be interpreted according to the risks of daily life. I reject the most prominent defense of daily life, which claims that daily risks are morally relevant because they replace, rather than add to, the risks a child would ordinarily face. Instead, I propose that these risks are part of a reasonable trade-off between personal safety and our ability to pursue meaningful lives. I then examine whose daily life should be captured in the concept of minimal risk. I reject arguments that minimal risk should refer to healthy children or the subjects of the research and propose instead that the referent should be children who are not unduly burdened by their lives. I argue that children are not unduly burdened when they fare well and defend the idea that children fare well when they possess sufficiently high degrees of the substantive goods of childhood. I conclude by analyzing a controversial case study using my interpretation of minimal risk. I draw on this case to argue that my interpretation offers clear guidance for research ethics review and contributes to a determination that is more plausible than its rivals. (shrink)