This article investigates the viscoelastic behavior of poly(acrylonitrile) (PAN) and poly[N-(4-carboxyphenyl)-maleimide] (PMI) solutions in dimethylformamide (DMF) in comparison with PMI/PAN/DMF ternary mixtures. Some theological characteristics, such as viscosity and relaxation time, were investigated as functions of the polymer mixture composition at different temperatures in the range of 0-60 degrees C. The solutions of each polymer and their mixtures exhibit a Newtonian behavior throughout the studied frequency range. At low temperatures, the behavior of the solutions having high PAN contents in the polymer mixture is influenced by physical gelation of the solution. The activation energy of the flow gives indications about the intensity of polymer polymer interactions as a function of the polymer mixture composition.