SrTiO3 dielectric ceramics were fabricated in air by using M2O3-CuO-PbO as dopants (M = Sm,Nd,La,Yb). The obtained ceramics exhibited a high dielectric constant (epsilon(25) > 4880) with stable temperature characteristics. With doping the rare-earth ions from Sm --> Nd --> La --> Yb, the corresponding dielectric constant regularly decreased. The investigation of microstructure showed that Yb additives benefited to the grain growth and CuO additives mainly segregated at the grain boundaries to form the insulation layers. According to the results, the conduction mechanism of SrTiO3-M2O3-CuO-PbO system was discussed. (C) 2004 Elsevier Ltd. All rights reserved.