The effect of different extraction procedures on the yields of water-soluble and water-insoluble glycogen fractions from a number of Saccharomyces strains was studied by using a specific method for glycogen determination. The similarity of the yields obtained by the different procedures showed that neither form of glycogen is an artifact, and variations in the relative amounts of glycogen in the two fractions during cell growth and in different yeast strains suggest that they represent different pools of storage material with specific roles in cell development and differentiation. A proportion of the water-insoluble glycogen fraction, solubilized by mechanical agitation, was shown to be strongly associated with a beta-glucan-like polysaccharide that may be a cell wall component.