Salivary cortisol levels were assessed in 19-month-old infants following the Ainsworth Strange Situation procedure. 38 infants participating in Project STEEP at the University of Minnesota served as subjects. Project STEEP is a longitudinal intervention program designed to promote healthy parent-child relationships and to prevent emotional problems among children born to mothers who are at high risk for parenting problems. Following the Strange Situation, saliva samples were collected and assayed for cortisol, a steroid hormone frequently examined in studies of stress. Behavior during the Strange Situation was coded by trained coders, and attachment classifications were determined for each infant. Cortisol concentrations did not differ between the 6 Avoidant/Resistant (A/C) and 17 Securely Attached (B) toddlers. Toddlers (n = 11) who were classified as having Disorganized/Disoriented (Type D) attachments exhibited higher cortisol concentrations than toddlers in the traditional (ABC) classifications. Results of this study were consistent with a model of stress reactivity that conceptualizes the organization of coping behaviors as a factor that mediates physiological stress responses.