The determination of the biophysical properties of polysaccharides is becoming increasingly important in commercial and pharmaceutical applications. molecular weights distributions, conformations, and size distributions are obtainable through experiments with analytical ultracentrifugation. These determinations can be difficult, however, due to the high thermodynamic nonideality and polydispersity with respect to both molecular weight and composition, as well as potential self-association commonly observed with these molecules in solution. Usually, a combination of complementary techniques are needed for the full understanding of the solution characteristic of the macromolecules. Although carbohydrates do not have a chromophore absorbing in either the ultraviolet or visible spectrum, optical systems based on refraction of light by the solute can be used for the study of the macromolecular characteristics. (1 yields 3)-(beta) -Glucans are known to exhibit immunomodulatory and biological activities. These activities are dependent on the conformational structure and molecular weight of the glucan. A soluble (1 yields 6)-(beta) - branched (1 yields 3)-(beta) -glucose homopolymer was isolated from the cell wall of Saccharomyces cerevisiae. In this paper we describe the preliminary characterization of a purified fraction from this soluble glucan measuring molecular weights using analytical ultracentrifugation, light scattering, and size-exclusion chromatography - and we explore the effects of temperature using these techniques.