An unexpected rise in cortisol across the day in full-day, center-based childcare has been recently observed. Most of the children in these studies exhibited the rise across the day at childcare, but the expected drop at home. Possible explanations include more or less napping at childcare than at home. This study measured cortisol during childcare at 10:30 a.m., pre-rest, post-rest, and 3:30 p.m. for 35 children, and at 10:30 a.m. and 3:30 p.m. at home for 8 children. Duration and quality of rest were coded during nap periods. For 91% of children, cortisol rose at childcare and for 75% dropped at home. None of the napping variables were related to the rise at childcare nor were differences found between home and childcare rest. Factors other than daytime rest periods seem likely to account for the rise in cortisol across the childcare day, possibly factors involving the interactional demands of group settings during this developmental period.