In this chapter, I will first describe a general model in which the reactivity and regulation of stress physiology serves as a common pathway through which many aspects of early adversity may converge. In this model, caregiving characteristics function to mediate and moderate the impact o f early adverse conditions on the activity of stress systems. After a brief discussion of the physiology o f stress, I re­ view the animal data that support this model and consider whether and how the animal models may need to be altered when researchers attempt to apply them to human development in adverse contexts. I then review the limited data available on human infants and children and argue that it is largely consistent with the pro­ posed model.