The low frequency dielectric dispersion of complex perovskite Pb(Fe 1/2Nb1/2)O3 sintered at different temperatures is carried out as a function of temperature. The sintered samples are annealed in oxygen atmosphere and the effect of annealing on the dielectric properties is investigated. The observed variation in the dielectric dispersion on annealing indicates that the oxidation state of iron plays a significant role in deciding the dielectric properties exhibited by this compound. The results are discussed in conjecture with variation in resistivity and density between the samples. © 2004 Elsevier B.V. All rights reserved.