Advances in cancer therapies have led to increasing numbers of adult survivors of pediatric malignancy. Unfortunately, treatment of childhood cancer continues to require agents designed to destroy malignant cell lines, and normal tissue is not always spared. While early treatment- related organ specific toxicities are not always apparent, many childhood cancer survivors report symptoms that interfere with daily life, including exercise induced shortness of breath, fatigue and reduced capacity to participate in physical activity. These symptoms may be a hallmark of premature aging, or frailty. Frailty is a phenotype most commonly described in older adults; it indicates persons who are highly vulnerable to adverse health outcomes. Frailty may help explain why nearly two thirds of childhood cancer survivors have at least one severe chronic health condition 30 years from diagnosis, why childhood cancer survivors are more likely than peers to be hospitalized for non-obstetrical reasons, and why they have mortality rates more than eight times higher than age-and-gender matched members of the general population.