The Children's Oncology Group (COG) is a National Cancer Institute (NCI) supported clinical trials cooperative group, and the world’s largest organization devoted exclusively to childhood and adolescent cancer research. COG’s goal is to cure all children and adolescents with cancer, reduce the short and long-term complications of cancer treatments, and determine the causes and find ways to prevent childhood cancer. COG unites more than 9,000 experts in childhood cancer at more than 200 leading children’s hospitals, universities, and cancer centers across North America, Australia, New Zealand, and Europe in the fight against childhood cancer. Today, more than 90% of children and adolescents diagnosed with cancer each year in the United States are cared for at Children’s Oncology Group member institutions. COG’s unparalleled collaborative efforts provide the information and support needed to answer important clinical questions in the fight against cancer. The Children’s Oncology Group has nearly 100 active clinical trials open at any given time. These trials include front-line treatment for many types of childhood cancers, studies aimed at determining the underlying biology of these diseases, and trials involving new and emerging treatments, supportive care, and survivorship.