Polycrystalline samples of Pb(Mg1/2X1/2)O-3 (X = Mo and W) were synthesized by a high-temperature solid-state react-ion technique. Preliminary structural (X-ray diffraction) study of the compounds shows the formation of a single phase compound, Microstructural study of the compounds shows a uniform distribution of nearly spherical grains throughout the surface of the sample. Detailed studies of relative dielectric permittivity (Er) and loss tangent (tan 3) of the compounds both as a function of frequency ( 10(2)-10(4) Hz) at room temperature (30degreesC) and temperature (30-320 degreesC) at 10kHz suggest that the compounds have anti ferroelectric phase transition. The activation energy of the Mo and W containing compound was found to be 0.61 and 0.72 eV, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.