Relationships among effortful control, parenting strategies, and social behavior were examined contemporaneously for 4- and 5- year- olds. Hierarchical multiple regression analyses indicated that parenting moderated the relationship between effortful control and social behavior, especially for 5-year-olds. In addition, the extent to which infant regulation and reactivity during a stranger approach situation and maternal sensitivity during play predicted rates of effortful control in early childhood was examined longitudinally in 39 participants. Hierarchical multiple regression analyses indicated that infants who showed more regulation during the stranger approach later showed higher effortful control scores, compared to infants who showed more reactivity to the stranger approach. Furthermore, maternal sensitivity during play in infancy predicted later effortful control in early childhood. Results are discussed in terms of self-regulation theory and the role of child factors and caregiver behavior in the development of regulation.