A flocculating strain of Saccharomyces diastaticus NRRL2416 was isolated after ethidium bromide mutagenesis and density gradient separation. Flocculation did not change the general characteristics of the strain. Flocculation was better on maltodextrin-containing media than on others. It was found to be calcium-dependent and sensitive to growth conditions. The deflocculating effects of some sugars suggested that mannose may be involved in the mechanism of flocculation, as for strains of the FLO1 phenotypic group.