Surfactants, i.e. surface active agents, are an important group of chemical compounds that are studied and applied to industry and in chemical laboratories. Presently, a tendency is observed to produce surfactants from renewable and biodegradable sources. Bio-surfactants constitute such a group; they, compared to synthetic surfactants, show a lower toxicity and a higher environmental compatibility. Bio-surfactants can be produced either using a biotransformation method or a fermentation process with the use of bacteria, yeast, or fungi. In this paper, the bio-surfactants are briefly described, the bio-technological methods of their synthesis are depicted, and, also, there are shown some selected trends in practical applications of surface active compounds.