AbstractYeast counts were made at intervals during fermentation of grape‐juice in the presence and absence of grape‐skins. Fermentation was apparent when the viable count was about 10 million cells/ml.Single‐colony isolates obtained by plating‐out the juices about midway through fermentation were tested for identity with the selected yeast‐starter added initially, using growth in the presence of actidione, frequentin, 8‐hydroxyquinoline and sorbic acid, appearance of giant colonies, maltose fermentation and appearance of growth in malt extract as criteria for comparison.In the white juice without grape‐skins 94%, and in the red juice with grape‐skins 81%, of the yeasts isolated could not be differentiated from the starter yeast added initially. The two dominance assessments differed significantly from one another.The significance of the results is discussed in relation to the use of selected yeasts in winemaking and the microbiological concept of dominance in mixed cultures.