The effects of composition on the physical property change in the phase coexistence region between the tetragonal and rhombohedral phases have been investigated as a function of zirconium concentration, x, for the MnO2-doped Pb(ZrxTi1-x) O3 (0.40 less-than-or-equal-to x less-than-or-equal-to 0.60) ceramics. The relative amount of phase coexisting between the tetragonal and rhombohedral phases affects greatly both dielectric and piezoelectric properties as a function of zirconium concentration. However, there are no detectable changes between the apparent density and microstructure. Also, in the coexistence region, the relative amount of coexistence of the rhombohedral phase increases with MnO2 addition. The inflection points of the dielectric constant shift to lower zirconium concentration in proportion to the MnO2 addition, owing to the substitution effect on the PZT lattice site.