Medicine is an ever-changing science. Microorganisms are the leading etiological agents in causing the many diseases in humans. In this book, we briefly reviewed the role of viral agents in causing periodontal diseases. Information from different sources was gathered and reviewed thoroughly in the literature regarding different viruses, their role in causing periodontal disease and precautions to be taken by the dentists to prevent the disease transmission are included. We brought the relevant and valuable information together in the form of this book. This book is much useful to know about the viral agents and their role in causing periodontal diseases for the undergraduates, postgraduates, and research scholars.