Antimicrobial peptides (AMPs), also called host defense peptides (HDPs) are part of the innate immune response found among all classes of life. AMPs have a broad spectrum of targeted organisms ranging from viruses to parasites. In this book we have tried to summarize the major types of AMPs, their modes of action, and the common mechanisms of AMP resistance along with the principles for designing effective AMPs and the future potential of using AMPs in periodontology.