The piezoelectric properties of rhombohedral relaxor-ferroelectric compositions close to morphotropic phase boundary have been studied as a function of temperature. As they exhibit, upon heating, a rhombohedral to tetragonal phase transition the piezoelectric behavior changed with temperature. Large piezoelectric (d(33)) and coupling (k(33)) coefficients of 0.91 Pb(Zn1/3Nb2/3)O-3-0.09PbTiO(3) single crystals drop to usual ceramic values after crossing the transition. Intrinsic and reversible contributions to the piezoelectric response reach a maximum at transition for 0.50PNN-0.16PZ-0.34PT. The influence of poling temperature on extrinsic contributions through possible structural changes was demonstrated.