In the present study a series of poly(vinyl pyrrolidone) (PVP) blends with a series of styrene-vinyl phenol copolymers (SVP) have been prepared and studied. Copolymers with a vinyl phenol content greater than 4 mol% show complete miscibility with PVP over the whole blend composition range. Copolymers containing more than 25 mol% vinyl phenol form complexes with PVP, which precipitate in solution with a common solvent. The miscibility was verified both by visual inspection of the blends and by differential scanning calorimetry measurements, which showed a single glass transition temperature (T-g) throughout the whole composition range. Unusually large positive deviations from linearity were observed in the T-g versus composition diagrams of some blends. The extensive hydrogen bonding interactions between the mixed polymers were studied by FTi.r. spectroscopy.