The International BFM Study Group (I-BFM SG) is dedicated to promote both research and clinical care for children and adolescents with leukemia and lymphoma. A growing number of participating national study groups from meanwhile more than 30 countries world-wide collaborates in committees and associated working groups addressing important aspects of clinical and basic research in the field of leukemia and lymphoma occurring during childhood and adolescence. The results are shared and discussed in meetings on a regular basis, guaranteeing fast and systematic transition of research findings to clinical care.The tradition of Biennial Childhood Leukemia Symposia (CLS) was established in the late 90s in Hannover, Germany. Since 2004, this symposia have been interconnected with the I-BFM-SG meetings (CLS takes places every other year), offering an unique chance to discuss the latest progress in childhood leukemia in an open forum of pediatric hematologists and oncologists from all over the world. The Symposium has a standard congress structure composed of single oral session, invited talks by top experts in the field are combined with free communications and poster session.