The stress response is initiated in the brain, which determines both the physiological and behavioral responses to an event. The normal physiologic response is complex and dynamic process by which the body responds to daily events in an effort to maintain equilibrium. If the stress becomes overwhelming for the individual, either due to the number or magnitude of stressors, the burden or overload can lead to dysregulation of biologic mediators and behavioral changes (poor sleep, eating or drinking too much, smoking, lack of physical activity) that can exacerbate disease (e.g. cardiovascular disease). A recent study in cancer caregivers demonstrated marked changes in neurohormonal and inflammatory processes in the year following a loved one s cancer diagnosis which may place the caregiver at risk for morbidity and mortality from disease. The relationships among the physiologic and psychological responses as well as behavioral changes to stress have not been explored in HSCT caregivers.