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 in clinical research. We propose 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; ethical considerations underlying study design, including clinical equipoise, placebo controls, and non-inferiority designs; the use of data monitoring committees; compensation; and parental permission and child assent to participate in research. We incorporate selected national (USA) and international guidelines, as well as regulatory approaches to pediatric studies that have been adopted in the USA, Canada, and Europe.