A review.Lantibiotics and other ribosomally synthesized peptides have attracted increasing attention in the search for new chem. classes of antibacterial agents effective against multidrug-resistant pathogens.Several factors have probably contributed to this resurgent interest.Among them, the realization that many different classes of ribosomally synthesized peptides were produced by almost all taxa of bacteria; that lantibiotics, being ribosomally synthesized, are amenable to the generation of analogs by codon substitutions in the structural gene; and that, by binding to biosynthetic intermediates and not directly to enzymes, resistance in bacterial pathogens cannot be simply acquired by mutations in the target enzymes.In this chapter, the authors will review the chem., biosynthesis, occurrence and mechanism of action of lanthipeptides, with particular focus on lantibiotics.The authors will also present three lantibiotics that are currently under advanced preclin. or early clin. development, as well as some recently discovered compounds which represent improved variants of known lantibiotics.