Currently, in the US and Western Europe about 75% of children diagnosed with cancer survive at least 5 years and most survivors are cured. Unfortunately, survivors are at an increased risk of a range of adverse health outcomes compared with that expected from the general population. Large-scale studies of mortality occurring beyond 5-year survival show that the majority of the deaths in the initial decade are because of recurrent tumors. Thereafter, other causes of death that occur increasingly including second malignant neoplasms, cardiac deaths and pulmonary deaths. During the past 25 years, research has focused on estimating the risks of such long-term 'effects' of childhood cancer and its treatment. Studies have examined how risks vary in relation to a range of factors that include treatment exposures, age at treatment, type of childhood cancer, duration of follow-up, and factors that may genetically predispose a survivor to particular complications. This information is critical to counsel survivors and their families in relation to long-term risks and identify specific groups of survivors who are at particularly high risk--with a view to earlier diagnosis or intervention and provide the means of assessing potential benefits and risks of different proposals for future treatment protocols.