The notion that negative childhood experiences can be sources of toxic stress that have short- and long-term consequences for children's health and well-being has gained increasing attention in recent years. The family environment can be a key source of stress, particularly when parents inflict pain on children; when that pain rises to the level of physical abuse the stress is thought to be toxic. In this article the author considers the possibility that nonabusive physical punishment may also constitute a source of toxic stress in the lives of children that affects their brain structure and functioning. The research linking physical abuse and physical punishment to children's brain structure and functioning is summarized, and the article concludes with a discussion of implications for future research, policy, and practice.