Sclerotan (SSG) was an extracellular polysaccharide from Sclerotinia sclerotiorum by submerged fermentation. It had potential immunomodulating and antitumor activity. The SSG was a glucan composed of beta-linked D-glucoses. It was hard to dissolve in water under normal condition, but its aqueous solution had fine rheological properties. Its intrinsic viscosity [eta] hardly changed with ionic strenth. Change of its [eta] value was not remarkable between pH 1.88-12.36. Nevertheless, when the pH came to 13.32, the [eta] value decreased rapidly due to change of molecules conformation. Effect of temperature < or = 90 degrees C and heat treatment on apparent viscosity of SSG solution was minor.