It has been shown that, to varying degrees, long-term survivors of childhood cancer are at risk of developing second cancers and of experiencing organ dysfunction, reduced growth and development, decreased fertility, and early death. The degree of risk of late effects may be influenced by various treatment-related factors such as the intensity, duration, and timing of therapy, as well as by individual characteristics such as the type of cancer diagnosis, the person's sex and age at the time of treatment, and genetic factors as indicated by for example, family history of cancer. The catalyzing goal of the Childhood Cancer Survivor Study (CCSS) was to assemble a cohort of survivors sufficiently large and diverse enough to enable investigators to characterize the experience of participants regarding these and other delayed effects of treatment. Further, investigators hoped to be able to gather information about the health-related behaviors and patterns of medical care use of survivors in order to facilitate the development of prevention strategies and the assessment of follow-up needs.