The polycrystalline samples of Pb(Mn1/4Cd1/4W1/2)O-3 were synthesized by a high-temperature solid-state reaction technique. A preliminary X-ray structural study of the compound at room temperature shows the formation of a single-phase compound with a non-centrosymmetric space group P222(1) of orthorhombic structure. Studies of dielectric constant (epsilon) and loss tangent (tan delta) both as a function of frequency (10(3)-10(4) Hz) and temperature (20-350 degreesC) suggest that the compound undergoes a phase transition at 250 degreesC and has a very high value of dielectric constant similar to30,000 at transition temperature. Both ac and dc conductivity have been studied over a wide range of temperature. The activation energy (E-a) of the compound was calculated from both the plot of ac and dc conductivity versus inverse of absolute temperature. Variation of dc resistivity with electric field (0.55-53 kV m(-1)) at room temperature and variation of dc resistivity (10(6)-10(3) Omega m) with temperature (26-350 degreesC) at a constant electric field of 11.2 kV m(-1) showed the semiconductor characteristics of the material. (C) 2002 Elsevier Science B.V. All rights reserved.