The purpose of this study was to examine individual differences in the activation and regulation of the hypothalamic-pituitary-adrenal (HPA) axis in prepubertal children after exposure to two different stress modalities and to evaluate the utility of an individual differences approach to the examination of HPA axis functioning. After a 30-min controlled baseline period, 73 7-year-olds (40 boys and 33 girls) were randomly assigned to a validity check condition or one of two experimental tasks designed to elicit fear or frustration. This was followed by a 60-min controlled regulation phase. A total of 17 saliva samples were collected, including 12 poststress samples at 5-min intervals. There was a significant stress modality effect, with children exposed to the fear condition reaching peak cortisol levels at 25 min poststress and those exposed to the frustration condition reaching peak levels at 45 min poststress. There was no difference in peak cortisol levels between the stress modalities. Individual variability across conditions was significant, with participants reaching peak levels as early as 10 min poststress and as late as 60 min poststress. Our data suggest that analysis of individual curves prior to making group-level comparisons may improve the explanatory power of HPA axis behavior models. (Contains 1 table and 2 figures.)