The development of self-regulation in early childhood is understood to be foundational for later cognitive and social development and early success in school. However, knowledge of relations among cognitive and social-emotional aspects of self-regulation in childhood and the relation of child characteristics and early experience to developing self-regulation is quite limited. Prior short-term longitudinal and cross-sectional studies have been conducted with relatively small and homogenous samples and employed a limited array of measures. To address the limitations of prior work, this competing continuation application for Project 1 of the Family Life Project program project will test a developmental psychobiological model of emeriging selfregulation in a population-based sample of 1,292 children and families in predominantly low-income and rural communities in North Carolina and Pennsylvania. Measures of observed emotion and stress reactivity collected in the first phase of our project at child ages 6, 15, and 24 months will be related to developmental trajectories for executive function (EF) and social-emotional self-regulation at time points ranging from age 36 months through the 2nd grade. Trajectories for EF and social-emotional self-regulation will then be related to measures of academic and social progress in school. A unique feature of this program project is the ability to place relations among early emotion and stress reactivity, developing self-regulation, and early school progress in context. We propose that the development of EF and social-emotional self-regulation will be most compromised in children characterized by high and sustained levels of emotional and stress reactivity during infancy and toddlerhood living in homes in which parenting and contextual risk is high and stable from infancy through the early school years. However, we also expect that this risk can be moderated by preschool and early school experiences that promote language development, foster supportive relationships with teachers, and promote early literacy and math abilities. By combining detailed assessment of emerging child self-regulation in Project 1 with the measurement of family processes in Project 3 and the measurement of child language development and the context of early schooling in Project 2, this program project provides an overall breadth and depth of measurement that could not be accomplished within the constraints of a single study.