The miscibility behavior of the blends of Polyetherimide (PEI) and Polystyrene (PS) was studied using different experimental techniques. The intrinsic viscosities were determined for different ratios of PEI/PS blend in dilute chloroform solutions at 25 oC using viscometry. According to different methods proposed by Huggins, Krigbaum and Wall, Catsiff and Hewett using the experimental results of the intrinsic viscosity studies of the PEI/PS blends, some miscibility parameters were obtained. Besides, the miscibility of the PEI/PS blends was studied using Fourier Transform Infrared Spectroscopy (FT-IR) and Differential Scanning Calorimetry measurements.