The last decade has seen a surge of interest in pediatric myelodysplastic diseases and a number of initiatives to improve registration,diagnosis, and management have been launched. An increasing number of publications have appeared but no book has as yet compiled the many aspects of myelodysplastic diseases in children.This book has contributions from the major researchers and groups involved in the study of myelodysplasia and myeloproliferative disorders in children. It is composed of three introducing chapters on classification and epidemiology followed by detailed discussion of the many aspects of MDS and JMML. The last chapters present the experiences from a number of study groups worldwide describing their achievements in the study of this intriguing group of diseases. The book reflects out current knowledge on myelodysplastic and myeloproliferative disorders including some controversies. In a field moving rapidly towards new accomplishments discrepancies in interpretation of the data will invariably exist.It has been a pleasure to collaborate with this distinguished group of authors. We hope hematologists, pediatric oncologists, and laboratorial professionals will find the book useful in clinical practice and an inspiring basis for further research.