Octahedral cations of M g and Ta in Pb[(Mg,,Ta, ~)~.~T i~.~] 0 , were replaced independently as well as simultaneously by Zn and Nb, respectively, to Investigate the effects of cornposition modification on phase formation and dielectric properties, When Mg was replaced by Zn, the perovskite formation yields decreased continuously to 0% with the Zn fraction. In contrast, nearly phase-pure perovskite powders could be prepared when Ta and the hfg-Ta complex were replaced by Nb and Zn-Nb, respectively. Dielectric relaxation with diffuse phase transition was observed at most of the compositions. Dielectrlc maximum temperatures increased steadily with the substituent fractions, whereas variations of the maxlmum dielectric constant were dependent heavily on the substituent species.