The polyetherimide/barium titanate (PEI/BaTiO3) nanocomposite films were successfully prepared by mixing the fine BaTiO3 particles into poly(amic acid) solution under ultrasonication followed by film casting and thermal imidization. Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure and properties of the obtained nanocomposites. The dielectric properties of the PEI/BaTiO3 nanocomposites were analyzed in detail with respect to different experimental parameters like frequency, ceramic concentration and temperature. In comparison with pure polyetherimide, the dielectric constant of the nanocomposite (50 vol.% BaTiO3) was significantly improved by twelve times while the loss tangent only increased five times. The nanocomposites exhibited good dielectric stability over a wide range of temperature and frequency. Different theoretical approaches have been employed to predict the effective dielectric constant of the nanocomposite systems and, the estimated results were compared with the experimental data. The piezoelectric coefficients of the nanocomposite films were measured with varying ceramic volume fractions. (C) 2010 Elsevier B.V. All rights reserved.