Dielectric and piezoelectric properties of the lanthanum-doped morphotropic phase boundary (MPB)composition in the Pb(Zn1,3Nb2,3) O-3-BaTiO3-PbTiO3 system have been studied. Compositions of the samples were intentionally modified so that the compensation for the charge difference between La3+ and Pb2+ ions was realized by the increased Zn/Nb ratio. The solid solubility limit of La2O3 is shown to be less than 5 mol% by X-ray diffraction analysis. Rhombohedral phase is increasingly stabilized against tetragonal phase with progressive incorporation of the dopant into the A-site of perovskite structure, alternatively. the location of the MPB composition range is shifted towards PT-rich end. Moreover, it was revealed that the lattice distortion of either tetragonal or rhombohedral phase can be reduced by La-doping. The dielectric permittivity maximum epsilon'(max) and the temperature of epsilon'(max) are remark' ably decreased by increasing La2O3 content, whilst the degree of the frequency-dispersion is slightly weakened. Both the degree of diffuse phase transition (DPT) and the non-Curie-Weiss behavior can be signtificantly promoted by La-doping. (C) 2002 Elsevier Science B.V All rights reserved.