What is clear from the literature is that caregiving is stressful, and it appears to increase one s risk for morbidity and mortality, particularly by increasing cardiovascular risk. What is less clear is what behavioral, psychological, physiological and clinical changes are associated with the process of caregiver for individuals undergoing allogeneic HSCT, a particularly long and stressful experience. The purpose of this exploratory, pilot study is threefold: to longitudinally examine physiological, behavioral and clinical factors in HSCT caregivers during the acute transplant recovery period, to compare those factors in HSCT caregivers to non-caregivers, and to explore the associations among physiological, psychological, behavioral and clinical factors in HSCT caregivers.