AbstractThe macromolecular compounds excreted during growth by yeasts as exocellular fractions were studied and found to contain a high proportion of carbohydrates. On the basis of the specificity of these fractions, an attempt was made to distinguish between nine strains of a single species of yeast—Saccharomyces cerevisiae.Each strain came from a different source. The electrophoretic patterns of the exocellular fractions tested made it possible to distinguish between the nine strains, on the basis of Lodder's criteria for the morphological and physiological identification of yeasts. We considered that strains giving exocellular fractions distinguishable by electrophoresis belonged to distinct clones. Consequently, this technique enables us to go further than diagnosis of the specie