Miscibility and thermal properties of blends of polystyrene (PS) with poly(5-benzoyl-2,6-dimethyl-1,4phenylene oxide) (BPPO) or poly(5-acetyl-2,6-dimethyl-1,4phenylene oxide) (APPO) were investigated using light scattering, FTIR spectroscopy, and thermogravimetric analysis. The optical clarity and light-scattering behavior showed that both BPPO/PS blends and APPO/PS blends cast from chloroform were miscible over the entire composition ranges in part because of the van der Waals interaction between the component polymers. The light-scattering studies showed that the miscibility of the APPO/PS blend is better than that of the BPPO/PS blend.