Book excerpt: Bacteriophages are viruses that infect bacteria; as such, they have many potential uses for promoting health and combating disease. This book covers the many facets of phage-bacterial-human interaction in three sections: the role and impact of phages on natural bacterial communities, the potential to develop phage-based therapeutics and other aspects in which phages can be used to combat disease, including bacterial detection, bacterial epidemiology, the tracing of fecal contamination of water and decontamination of foods.