Technical Abstract: Bacteriophage are viruses that infect and utilize bacteria as their host. They can reside in the bacterial genome as a prophage, or enter the lytic phase, take over the host gene expression machinery, synthesize new phage particles, lyse the host, and release up to hundreds of phage progeny. Lysis occurs during the late phase of the lytic cycle when the phage endolysin and a holin molecule are produced. The holin creates holes in the cells lipid bilayer allowing the phage endolysin (peptidoglycan hydrolase) to escape and degrade the structural portion of the cell wall. These (and other phage encoded proteins) have been shown to inhibit bacterial growth. The ability to inhibit growth or kill bacteria make the bacteriophage and their gene products a rich source of potential antimicrobials. This review summarizes the recent resurgence of bacteriophage and their gene products as diagnostic and therapeutic agents and identifies recent patents that describe this technology. [Although Phage Display utilizes bacteriophage expression libraries to identify essential protein-protein interactions involved in infectious disease, this technology is omitted from this review.]