Biosurfactants, tensio-active compounds produced by living cells, are now gaining increasing interest due to their potential applications in many different industrial areas in which to date almost exclusively synthetic surfactants have been used. Their unique structures and characteristics are just starting to be appreciated. In addition, biosurfactants are considered to be environmentally “friendly,” relatively non-toxic and biodegradable. This Microbiology Monographs volume deals with the most recent advances in the field of microbial biosurfactants, such as rhamnolipids, serrawettins, trehalolipids, mannosylerythritol lipids, sophorolipids, surfactin and other lipopeptides. Each chapter reviews the characteristics of an individual biosurfactant including the physicochemical properties, the chemical structures, the role in the physiology of the producing microbes, the biosynthetic pathways, the genetic regulation, and the potential biotechnological applications.