The miscibility of amorphous, vinyl polymers depends upon the molecular weights and tacticities of the blend components. In this investigation blends of polystyrene (PS) and poly(vinyl methyl ether) (PVME) were studied. Three isotactic poly(vinyl methyl ether) (PVME) samples, synthesized in our laboratories, and one heterotactic PVME sample have been characterized by GPC, NMR, X-ray diffraction, and DSC. Atactic PS of three molecular weights were used. Cloud-point measurements were made with a light scattering apparatus. It was found that isotactic PVME is less miscible with atactic PS than heterotactic PVME.