The Children's Cancer Study Group is a multi-disciplinary organization formed to co-operate in research on malignant disease in children: specifically to study the factors which may cause or influence these diseases, and to develop, evaluate, and improve methods of treatment. The primary objective of the co-operative group has been the evaluation of new biological and chemotherapeutic agents in the treatment of acute leukemia and solid tumors in childhood, and to find new and better ways of using the already known agents. This evaluation is done by Pediatric Oncologists, surgeons, radiotherapists, pathologists and immunologists within the co-operating institutions which make up the group. It is also our objective to provide supportive care for these children with leukemia and solid tumors which will enable all children who desire to participate in our protocol studies regardless of the social or financial background of their families, and then to evaluate the effect of this supportive care on their longevity and their well being. This supportive care includes financial supportive care (domicillary care, travel assistance, out-patient costs, etc.), social service assistance, as well as medical supportive care.