Dr. Pettigrew discusses the emerging therapeutic science of bacteriophages, viruses that infect and replicate within bacteria. Although these organisms have been utilized as antibacterial therapies for decades in some regions of the world, they are relatively unknown in western medicine. They may show promise in the treatment of resistant bacteria, as alternatives to antimicrobial compounds, in the preservation and sterilization of food products, in the defense against bioweapons and in environmental antisepsis.