Deposition of thin films of the solid electrolyte Ag7I4VO4 by an electrodeposition technique is discussed. The X-ray diffraction technique has been used for the characterization of the films. Measurement of a.c. electrical conductivity in the temperature range 300-400 K showed that films deposited at 313 K and at a current density of 8 mAcm-2 are of the best quality, having a typical conductivity of 1.5 x 10-3Ω-1cm-1 at room temperature (305K) with an activation energy of 0.2eV. Dielectric studies carried out on the best quality films showed that Ag7I4VO4 possesses a high value of dielectric constant (∼ 105). The frequency dependence of the dielectric constant is explained as due to an interfacial polarization phenomenon. The behaviour of the dielectric ion suggests a Debye-type relaxation. © 1987 Chapman and Hall Ltd.