Differential scanning calorimetry, (DSC) and inverse gas chromatography, (IGC) were used to analyze the miscibility and interactions in the poly(4-hydroxystyrene)/poly(vinyl methyl ether) (P4HS/PVME) system. The miscibility was assessed by the measurement of a single glass transition temperature, T-g, for each blend composition. The T-g-composition curve was analyzed in terms of Fox, Gordon-Taylor and Kovacs theories. The influence of molecular weight of P4HS in the presence of a cusp in the T-g-composition curve was discussed by comparison with previous T-g data. The IGC retention behaviour of the homopolymers and three blends (0.25, 0.5 and 0.75 P4HS volume fractions) was realized at 190 degrees C using selected probes. The polymer-polymer interaction parameters chi(23) calculated from the Scott-Flory-Huggins formalism showed an apparent dependence on the probes. This dependence was analyzed using Horta＇s method based on the equation-of-state theory and a more simplified method proposed by Desphande. Negative values of chi(23) confirmed the miscibility of the system. A blend composition dependence of chi(23) was found, mainly determined by differences in the molecular surface-to-volume ratio of the polymers.