Two to three decades ago, multiple primary malignancies (MPM) were considered to be simply a clinical curiosity, with sporadic reports, mostly single case descriptions, found in the literature. While in the last few years, analyses of larger series have been published, the number of cases has still been relatively small and most of the reports have addressed a single type of primary tumor and its associations. With the improved prognosis and survival of cancer patients, MPM is becoming increasingly prevalent in this population, necessitating a better understanding of the characteristics and associations of the malignancies involved. Thus, as a prerequisite, a universal definition and an internationally accepted classification system, based on chronological, pathological, clinical, and other parameters, are needed. Moreover, much remains to be learned about the etiology of MPM, whether genetic, iatrogenic, or environmental. Several of the hereditary syndromes, such as familial adenomatous polyposis, hereditary non-polyposis colorectal cancer, hereditary breast-ovarian cancer, and multiple endocrine neoplasia, are already well-known and their characteristics in relation to MPM must be kept in mind. Nonetheless, along with these syndromes, there are sporadic and apparently casual associations between primary neoplasms that can involve almost any part of the body. This volume points out the clinical aspects of MPM and discusses the diagnostic and therapeutic problems that are encountered in treating these patients. "DNA-guided" surgery, currently confined to the treatment of patients with hereditary syndromes, will, along with other novel treatment strategies, no doubt play an increasingly greater role in the therapy of MPM. This work presents state-of-the-art information about MPM that is aimed at a broad range of medical specialists, including surgeons, endoscopists, oncologists, and geneticists,. The goal is to improve our understanding of this group of diseases as well the treatment of these patients.