The external electric and mechanical fields applied at angles to the initial poled direction of the ferroelectric ceramics produce a significantly different nonlinear behavior to that of external fields applied parallel to the poling direction. This angle dependent response of ferroelectric single and polycrystals are predicted by the model proposed based on irreversible thermodynamics and physics of domain switching. The dissipation associated with boundary constraints in thin ferroelectric single crystals are incorporated in the model. As well, the pressure dependent constraints imposed by the surrounding grains on the grain of interest at its boundary during domain switching is correlated with the resistance experienced by a ferroelectric single crystal on its boundary during domain switching. Taking all the domain switching possibilities, the volume fractions of each of the variants in a grain are tracked and homogenized for macroscopic behavior. Numerical simulations were carried out for the multiaxial behavior of ferroelectric single and polycrystals under electrical, mechanical and electromechanical loading conditions. © 2008 Elsevier B.V. All rights reserved.