Distant metastases are the main cause of cancer-related death. The onset of the metastatic process can now be assessed in cancer patients by the use of immunocytochemical and molecular methods that allow the identification of disseminated carcinoma cells in regional lymph nodes, peripheral blood or distant organs. There is increasing evidence that the detection and characterization of tumor cells present in bone marrow or peripheral blood can provide clinically important information. In this book, leading experts in the area of micrometastasis research provide an overview that summarizes the current state of research on micrometastatic disease in patients with solid tumors. In each chapter, the technical aspect as well as clinical relevance of micrometastasis detection is discussed. The book addresses basic researchers as well as clinicians involved in the treatment of cancer patients.