Since children are considered incapable of giving informed consent to participate in research, regulations require that both parental permission and the assent of the potential child subject be obtained. Assent and permission are uniquely bound together, each serving a different purpose. Parental permission protects the child from assuming unreasonable risks. Assent demonstrates respect for the child and his developing autonomy. In order to give meaningful assent, the child must understand that procedures will be performed, voluntarily choose to undergo the procedures, and communicate this choice. Understanding the elements of informed consent has been the paradigm for assessing capacity to give assent. This method leaves the youngest, least cognitively mature children vulnerable to waiver of assent and forced research participation. Voluntariness can also be compromised by the influence of authority figures who can exert undue influence and coerce children to participate in research. This paper discusses factors that may influence the decision to give assent/permission, potential parent-child conflict in the assent/permission process and how it is resolved, and potential parental undue influence on research participation. These issues are illustrated with quotations drawn from a larger qualitative study of parental permission and child assent (data not presented). We suggest a developmental approach, viewing assent as a continuum ranging from mere affirmation in the youngest children to the equivalent of the informed consent process in the mature adolescent.