The use of gel permeation chromatography (GPC) coupled with the multiangle laser light scattering (MALLS) detector for the determination of molecular weight and size distribution and for the identification of polymer branching is demonstrated on several examples of both organic and water soluble polymers. The influence of the second virial coefficient and the way of the light scattering data evaluation on the results obtained is shown. Measurements of the root mean square radius are presented for two series of polystyrene and polymethylmethacrylate standards, and the results are compared with the radii calculated from the Flory-Fox equation.