Background As observed in depressed adults, there is considerable variability in the degree and direction of hypothalamic-pituitary-adrenal (HPA) dysfunction in depressed adolescents. The variability in HPA findings may be attributed to experiential factors. Methods A modified version of a standard psychosocial stressor used in adults, the Trier Social Stress Test (TSST), was administered to 30 adolescents with major depressive disorder and 25 healthy adolescent volunteers. Cortisol concentrations were measured in saliva samples collected before and after the stressor. Information also was gathered on early and recent adverse experiences with standard interviews. Results Participants from both groups had increased cortisol secretion in response to TSST. Compared with controls, depressed subjects showed more elevated and prolonged cortisol secretion in response to TSST. The combination of early-life adversity and high levels of chronic stress during adolescence was the most powerful predictor of enhanced adrenal response to the TSST. Conclusions These results support previous findings on the role of experiential factors on HPA response to stress and in the development of mood disorders. Dissection of the heterogeneous pathophysiology of adolescent depression will assist in developing more specific interventions for different subgroups of patients.