Recent advances in the fields of molecular biology and epidemiology have led to significant development of studying revelations between infectious agents and cancer, and provide valuable insights into the molecular basis of carcinogenesis. Since the first oncogenic virus was discovered by Rous in 1911, many infectious agents including viruses, bacteria, and parasites are known to associate with about onefifth of all human cancers worldwide. Their impact on global health is significant. Despite that the link between cancer and microbe infection has been recognized in chickens over ten decades ago, the mechanistic basis for cell transformation became clearer until 1970. The discoveries of oncogenes/proto-oncogenes and tumor suppressors, as well as insights into cell growth factors, cell cycle regulation, checkpoints, and their operative protein factors, further promoted the understanding of infectious agents-associated cancers. Today in 2017, although close association between viruses and cancer has been established only in seven human viruses (HBV, HCV, HPV, HTLV, EBV, KSHV, and MCV), other infectious microbes including HIV, bacteria (H. pylori), parasites (blood flukes/liver flukes), and prions as presented in many of the chapters in the book illustrate a potential association with a variety of human cancers. The interplay between microbes and various microenvironment factors, including stress, inflammation, and deregulation of immune responses, is currently a hot topic in the field of microbe-related cancer. A few important scientific concepts detailed in the various chapters include the animal tumor models, the coinfection of different microbes, the interplay between microbe and microenvironmental stress, the multistepped process for cell transformation caused by infectious microbe, and the common and various mechanisms used by different types of infectious microbes. From such mechanistic and translational research, we hope that safe and more effective therapeutic drugs or vaccines against specific cancers will ensue in the future. This book emerged from a desire to provide an up-to-date progress of human cancers and their infectious causes. The editors have made great efforts to bring together teams of expert authors from all aspects of infectious microbes associated with cancer in this book. As tumor virologists, they have personally witnessed many pivotal advances in infectious causes of human cancers. It is therefore appropriate