Polycrystalline Zr-modified Sr5LaTi3Nb7O30 compound was prepared by a high-temperature solid-state reaction technique. X-ray structural analysis confirmed the formation of compound in an orthorhombic system at room temperature. Detailed studies of the dielectric parameters (dielectric constant and tangent loss) as a function of frequency (1-100 kHz) at different temperature (150 to 650 K) were carried out. It was found that as Zr+4 concentration increases in Sr5LaTi3-xZrxNb7O30, the value of dielectric constant decreases. These compounds show ferroelectric-paraelectric phase transition of diffuse type at 283, 305 and 320 K for x = 0, 1 and 2 respectively. The transition temperature (T-c) shifts towards higher temperature and maximum dielectric constant value (epsilon(max)) decreases with increasing Zr+4 concentration for x = 0 to x = 2. When Ti+4 cations were completely replaced by Zr+4 cations (i.e., Sr5LaZr3Nb7O30), the compound does not show any phase transition. Impedance-spectroscopic studies provided an insight into the electrical properties and understanding of relaxation behavior of the material. Measurement of electrical conductivity as a function of temperature suggests that the compounds have a negative temperature coefficient of resistivity (NTCR) with a typical semiconductor behavior. (C) 2004 Kluwer Academic Publishers.