This study examined associations between caregiver sensitivity and responsiveness in child care experienced at age 4 and children's effortful control skills at age 5, among 154 preschoolers who attended community-based child care settings. Sensitive caregiving was measured using a modified version of the Observational Ratings of the Caregiving Environment and children's effortful control skills were assessed using both a parent questionnaire and a laboratory assessment. Results suggest that effortful control is sensitive to thresholds of caregiver sensitivity. Specifically, positive associations between caregiver sensitivity and effortful control skills a year later were observed only for children in settings with relatively high-quality caregiver sensitivity. These findings suggest that supporting the development of children's effortful control skills may require exposure to child care that exceeds typical levels of caregiving quality experienced by young children in the United States. (author abstract)