This book provides a key for students to open the door to medical molecular virology, and therefore it only introduces the important themes of medical molecular virology. Questions are included between sections in all chapters, but with no "standard" answers. These questions are raised to prompt active and innovative discussion.The contents of this book are divided into two parts. The first 9 chapters introduce the important aspects of general medical molecular virology. Some chapters ask questions like "What is a virus?" "Are virus and cells interdependent?" "Is persistent virus infection a favorable balance?" "Why are there so many types of illterferons?" "Why is virus nomenclature important?" Other chapters describe viral oncogenesis,antiviral development, vaccines and prions. The latter three chapters describe selected individual viruses, which cover the RNA viruses(influenza virus, enteroviruses, Hantaan virus and flaviviruses), the RNA-DNA intermediate viruses (human immunodeficiency virus and hepatitis B virus), and DNA viruses (herpesviruses, human papilloma viruses,adenoviruses and poxviruses).It is hoped that by reading this book and by participating in discussions,the students will be interested in a further reading, and a list of reading materials is suggested at the end of each chapter.