The question of when and how to obtain child assent for nontherapeutic research has received increasing attention in recent years. Although child assent and parent permission are grounded in the principle of respect for persons, assent is often understood from the more narrow principle of respect for autonomy. When viewed in this way, "assent" is frequently conflated with "consent," and children are held to a higher standard than what might be sufficient for meaningful involvement in decision-making about research participation. When nested within the requirement for parental permission, child assent functions as a way to promote children's moral growth and developing autonomy, rather than as an autonomous decision. A developmental approach to child assent is necessary to understand how children can be meaningfully involved in decision-making about research participation across development. This approach suggests that the content and process of child assent should be allowed to vary across development. In addition, a developmental approach requires that future research employ longitudinal designs, examine the developmental mechanisms underlying age variations in child assent, and attend to both cognitive and noncognitive variables that may influence the assent process as children mature.