Much research has shown that acute and chronic stress can deleteriously effect physiological stress responses and mental health. However, recent research indicates that certain psychological factors can act as stress-protective resources. The proposed program of research focuses on the role of the self in reducing stress and mental illness, by testing how value-affirmations reduce acute and chronic stress responses, and depression and anxiety. Study 1 tests if a value-affirmation manipulation reduces college students' state anxiety and cardiovascular/neuroendocrine responses to an acute stress task. Study 2 will test longitudinally how a value-affirmation manipulation affects breast cancer patients' depression, trait anxiety, stress appraisals, and neuroendocrine reponses to radiation treatment. Both studies will test how self-resource variables affectively (e.g., feelings of self-worth) or cognitively (e.g., appraisal) mediate the relationship between value-affirmations and stress. In conducting these studies, this program of research will more clearly define the role of the self in reducing mental illness and individuals' psychological and biological responses to acute and chronic stressors.