Miscibility studies of unsaturated polyester resin-poly(methyl methacrylate) (UPR-PMMA) blend in chloroform were carried out in different percentages of the blend components. The viscosity, ultrasonic velocity, and refractive index methods were employed for the miscibility studies at 300C. The interaction parameters have been obtained using the viscosity data to probe themiscibility. These values indicated that the UPR-PMMAblend ismiscible. This was confirmed by the ultrasonic velocity and refractive index methods.