Presented here are recent findings on bacteriocins: plasmid-encoded toxins produced by bacteria, which differ from traditional antibiotics in killing only bacteria that are closely related to the producing strain. Included are introductory chapters on bacteriocins, microcins (low molecular weight bacteriocins), and lantibiotics (peptide antibiotics containing lanthionine), further, contributions on pore forming bacteriocins, the mechanisms of immunity to bacteriocins, uptake and secretion, as well as evolution of bacteriocins. It is of particular interest that the lantibiotic nisin is approved for use as food preservative and another lantibiotic, epidermin, has potential as a therapeutic drug against acne.