The minimal risk standard allows institutional review boards (IRBs) to approve pediatric research when the risks do not exceed the risks children face in daily life or during routine examinations. The fact that the risks children face in daily life vary with age raises the question of whether IRBs should implement this standard by adopting 1, 2, 3, or even more risk standards. The level of research risks to which it is appropriate to expose children depends on their maturity level. While younger children should be exposed to only very low research risks, it can be appropriate to expose older children to somewhat higher risks. This analysis supports 2 thresholds for minimal risk in pediatric research: one for research with younger children and a distinct standard for older children who can understand and who agree to participate.