The associative behavior of amphiphilic polysaccharides derived from dextran, a neutral bacterial polysaccharide, is studied in dilute and moderately concentrated aqueous solutions using viscosity measurements. It is shown that the viscosity of the aqueous solutions can be conveniently depicted over a wide concentration range by several semiempirical equations. The Martin equation as well as the Matsuoka-Cowman equation is shown to depict conveniently the experimental results. These two equations involve only viscometric parameters determined in the dilute range (intrinsic viscosity and Huggins constant). The modification of Lyons and Tobolsky is discussed. The Fedors equation is shown to be similar to the Heller equation over a large concentration domain. Their respective empirical parameters are correlated and can be calculated from the Huggins coefficient.