An improvement in gel permeation chromatography for polymer characterization has been effected by combining it with an automatic viscometric technique. This allows not only determination of the molecular weight distribution but also the intrinsic viscosity for any kind of homopolymer. Moreover, it permits determination of the viscosity–molecular weight relationship for linear polymers and the degree of branching for branched polymers. The use of this technique, coupled with UV or IR spectrometric measurements, provides information with respect to composition and molecular weight distribution in the case of copolymers. It is thus possible to characterize copolymers from the double point of view of composition and molecular weight polydispersity.