Heterogeneity in individuals' physiological stress responses is central to theories linking stress with vulnerability to disease. Although multiple cortisol profiles have been reported in response to acute psychological stress, most prior work focuses on a single, average pattern and relative deviations from it, such as greater or lesser response peaks or reactivity. The present aims were to identify cortisol stress response trajectory classes using a data-driven approach and test whether social-evaluative threat (SET), a reliable elicitor of cortisol, predicted a greater likelihood of membership in the more reactive profiles. Data were pooled from 13 acute laboratory stressor studies from two geographically distinct U.S. university communities. Participants included 1,258 adults ranging from 18 to 52 years (