The study of genitourinary tumors is an area of recent rapid growth both in the understanding of disease processes and in the development of new diagnostic and therapeutic modalities. During rapid growth phases within any field, it is desirable to reflect on the current 'state of the art'. It is difficult even for experts in reputed areas of advancement to distinguish true advances from false leads, but it is far more difficult yet for those whose expertise lies in other areas to evaluate important advances. Thus, an objective assessment of evolving areas of investigation in the form of a comprehensive review is of considerable value. we have attempted to provide the reader with an over­ In this volume, view of some of the current areas of investigation in urologic oncology by experts in each area. There often is a tendency for invited papers in books of this nature to lack important critical peer review and therefore, suffer from a lack of objectivity. We have attempted to diminish this problem by the selection of two experts to discuss each subject. We believe that this format has improved the overall quality of the book for two reasons: 1) the know­ ledge of each contributor that his or her work would be reviewed by a peer 2) the fact that contributions by encourages more rigorous scholarship, and two experts, including the individual insights of each, provides a better per­ spective for the reader.