Book excerpt: Cationic antimicrobial peptides are multifunctional peptides of the innate immune system, which not only act directly against microorganisms, but also signal between early and late immune responses and modulate inflammatory reposnes. The significance of these host defence peptides in combating infection and in host-microbe homeostasis has become increasingly clear, through advances made by microbiologists, biochemists, biophysicists, immunologists, molecular biologists, and a range of medical and pharmaceutical researchers. This book, drawing together contributions from leading scientists, reviews significant recent advances in our knowledge of mammalian antimicrobial peptides. In addition to providing up-to-date overviews of their structure, expression and biology, their multiple activities and interactions with microbial populations as well as their potential application as novel therapeutic agents are summarized. Chapters describing developments using animal models and investigations of the roles of these host defence peptides in microbial infections are complemented by chapters addressing their mechanisms of action and of microbial resistance.