The room temperature phase diagram of PUT, (Pb,La)(Zr, Ti)O-3, or L/Z/T for L < 12 and T < 10 was constructed using X-ray diffraction patterns of sintered and crushed PLZT material. The orthorhombic anti ferroelectric phase, a tetragonal phase, the rhombohedral (hexagonal) ferroelectric phases, and the mixed La-rich zone were identified. Increasing substitution of La for Pb in the structure of orthorhombic PLZT leads to a change toward the cubic structure with less anisotropy in a direction corresponding to the cubic 200 direction. At La above similar to 8 to 11 mol%, La2Zr2O7 appears in the mixed zone. With increasing substitution of Ti for Zr, there is no change toward a cubic structure as the anisotropy is nearly unchanged. However, at a Ti substitution above similar to 6 mol%, a rhombohedral and a tetragonal structure appear.