Melt blends of poly(methyl methacrylate) (PMMA) with a phenoxy (polyhydroxy ether of bisphenol A) have been prepared over the complete composition range using a single-screw extruder. Injection-moulded specimens of the blends were transparent, and differential scanning calorimetry and rheological measurements gave a single glass transition temperature (T-g), indicating miscibility of the blends. The plot of measured T-g versus composition showed negative deviation from additivity, except for the 10/90 (PMMA/phenoxy) blend which showed a positive one. Fourier transform infra-red spectroscopy showed that the maximum peak around 3400 cm(-1) moved towards a higher frequency in the blends, suggesting that intercomponent hydrogen bonding exists. Tensile properties (modulus, strength and elongation at break) of the blends showed a negative deviation for PMMA-rich compositions, and a positive deviation or followed simple additivity in phenoxy-rich blends. The blends were also miscible in the melt state, and a viscosity rise over log additivity in phenoxy-rich compositions strongly suggested chemical reactions between the ester groups of PMMA and hydroxy groups of the phenoxy polymer in these compositions.