Complete remissions and survival times of tumor patients are increasing steadily - and so is the risk of developing therapy-associated secondary malignancy. At the same time, we face the growing diagnostic and therapeutic problem of tumorigenesis during posttransplantation immunosuppressive therapy. The theoretical section delves into the various causes of tumorigenesis, with special chapters on secondary chemo- and/or radiotherapy-induced tumorigenesis and neoplasia occurring during posttransplantation immunosuppressive therapy. The risk of individual cytostatic agents causing secondary malignoma is covered, as are the functions and dysfunctions of immunosurveillance. The immune system’s methods of recognizing tumors are also examined, and specific information on the role of herpesviruses in organ transplantation is included. The clinical part of the book portrays in depth major hematologic and oncologic malignancies that can arise after chemo- and/or radiotherapy administered after organ transplantation. With this book, clinical hemato-oncologists and those working in transplantation will gain greater insight into the risks, genesis and complications of secondary malignancy - but also into its treatment today and in the future. Last but most certainly not least, the importance of international collaboration for the advancement of diagnosis and therapy is underscored - as is reflected by the international team of contributing authors.