Twenty years ago when Children's Cancer Association of Japan was born, the diagnosis of childhood leukemia amounted to a death sentence. Only 20% or so of children with leukemia survived more than 5 years. Since then, enormous improvements have been achieved regarding our understanding on the etiology, diagnosis, and the treatment of childhood leukemia. Now, 70% of children with leukemia survive and enter adult life. Even though the improved survival rate of children with leukemia represents a medical success story, we now face new problems. The first problem is the fact that we still lose...