Thin films of the solid solution lead magnesium niobate with lead titanate (PMNT) have been successfully grown using r.f. magnetron sputtering onto Si/SiO2 and SrTiO3 (STO) substrates and their structural, electrical and piezoelectric properties have been evaluated. In order to increase the piezoelectric properties PMNT thin films, our objective was to obtain highly textured films; even epitaxial films. To obtain epitaxial films it is necessary to have an epitaxial bottom electrode or a monocrystalline substrate. Thus, it is very difficult to grow epitaxial films when using directly a Si/SiO2 substrate (without buffer layer), so we have instead chosen to use an SrTiO3 Substrate. To demonstrate that the film's crystallinity influences the electrical films properties we measure the polarisation, dielectric constant and piezoelectric properties. Results are presented for the composition PbO+ MgNb2O6+MgO+TiO2 grown on Si/SiO2 and STO. We conclude that the epitaxial nature of the films improve the piezoelectric and dielectric response. It is the first time that such a comparison is made; the piezoelectric performances of the epitaxial PMN-T films on STO are the best in comparison with results published in the literature. (C) 2008 Elsevier B.V. All rights reserved.