In the United States, more than 10 000 children each year receive a diagnosis of cancer. Fortunately, cancer treatments have improved. More than 80% of children who receive a diagnosis of cancer survive at least 5 years after the diagnosis, and many live to adulthood. However, cancer treatments have side effects that cause serious health problems, such as heart conditions or secondary cancer. As more children survive cancer, more information is needed about their health over their lifetimes.