The transition to out-of-home child care brings a number of challenges for children, including complex peer interactions and extended separations from parents. Children often show a midmorning to afternoon rise in cortisol on child-care days, compared to the typical diurnal decline seen at home. Changes in cortisol were examined in a wide age range of children (N = 168; 1.2 months to 8 years, M = 3.27 years) during the 10-week transition to a new child-care setting. Structural equation modeling using latent change scores showed that children experienced an increase in the cortisol rise at child care across the 10-week transition. Furthermore, child age moderated the difference between home- and child-care cortisol patterns. Findings are placed in a developmental context, and potential implications and future directions are discussed. (author abstract)