The critical need for pediatric research on drugs and biological products underscores the responsibility to ensure that children are enrolled in clinical research that is both scientifically necessary and ethically sound. In this chapter, we review key ethical considerations concerning the participation of children. We review a basic ethical framework to guide pediatric research, and suggest how this framework might be operationalized in linking science and ethics. Topics examined include: the status of children as a vulnerable population; the appropriate balance of risk and potential benefit in research; and parental permission and child assent to participate in research.