Dilute solutions of glycogen from mussels (shellfish) and of different degradation steps were investigated by static and dynamic light scattering, viscometry, and end group analysis of the reducing end. The data were analyzed in comparison with theory for hyperbranched polymers. In the monomer of the A <(B1)(B2) type, the functional group B-2 (resulting in alpha(1, 6) linkages) has a much lower reactivity than that of the B-1 group (leading to alpha(1, 4) linkages and chain growth). Qualitative agreement in behavior was found with the nonfractionated samples, but the effective branching density, derived from the applied physical techniques, was found to be considerably lower than that known from chemical analysis. SEC fractionation in on-line combination with multiple-angle laser light scattering and a viscosity detector revealed molar mass distributions that are composed of two main components. These components differ in their physical properties. The required examination was possible because R-g and [eta] could be measured for each slice. Shrinking factors g = R-g(b)2/R-g(lin)2 and g＇ = [eta](b)/[eta](lin) were determined. The results of quantitative analysis are discussed in relation to current theories.