X-ray diffraction patterns of Pb(Zr0.3Ti0.7)O-3 and Pb(Zr0.7Ti0.3) O-3 have been measured at pressures up to 36 GPa with good signal-to-noise ratio using synchrotron radiation. In order to re. ne the crystal structure, Rietveld analysis has been performed. The structure of Pb(Zr0.3Ti0.7)O-3 is tetragonal in space group P4mm with lattice parameters a = b = 3.9843 +/- 0.0003 A and c = 4.1545 +/- 0.0003 angstrom at ambient pressure. A pressure-induced phase transition was found in the pressure range higher than similar to 7.4 GPa at room temperature. The high-pressure phase is cubic in space group Pm (3) over barm with lattice parameter a = 3.9600 +/- 0.0003 angstrom at 7.4 GPa. The Birch-Murnaghan equation of state fit to the experimental data yields B-0 = 83.9 +/- 1.7 GPa (B-0' = 4.0 is fixed) for tetragonal phase and B-0 = 102.5 +/- 4.4 GPa (B-0' = 4.0 is fixed) for cubic phase with V-0 = 65.95 +/- 0.01 angstrom(3). The structure of Pb(Zr0.7Ti0.3)O-3 is monoclinic in space group Cc with lattice parameters a = 10.0627 +/- 0.0164 angstrom, b = 5.8511 +/- 0.0024 angstrom, c = 5.7949 +/- 0.0020 angstrom, and beta = 125.185 +/- 0.119 degrees at ambient pressure. No pressure-induced phase transition for Pb(Zr0.7Ti0.3)O-3 was observed over the pressure range of this study. The Birch-Murnaghan equation of state fit to the experimental data yields B-0 = 73.6 +/- 18.9 GPa (B-0' = 4.0 is fixed) with V-0 = 278.81 +/- 0.63 angstrom(3).