As a first step towards developing accurate constitutive relations for ferroelectrics, neutron diffraction experiments were conducted on Pb(Zr,Ti)O(3) (PZT)-based polycrystalline ceramics. Elastic lattice strain and texture evolution were monitored in situ during uniaxial compression experiments. Single phase (tetragonal) PZTs as well as those at the morphotropic phase boundary (with tetragonal and rhombohedral phases present) were investigated.