The electric field dependence of the piezoelectric properties of rhombohedral 0.955Pb(Zn1/3Nb2/3)O3–0.045PbTiO3 crystals were investigated as a function of orientation with respect to the prototypic (cubic) axes. For <111> oriented fields, depolarization and subsequent domain reorientation resulted in an apparent maximum in the piezoelectric coefficients occurring at ∼5 kV/cm, followed by nonhysteretic dij saturation, indicating a single domain state under bias. By extrapolation, single domain values for the piezoelectric coefficients d33 and d31 were determined to be 125 and -35 pC/N, respectively. The hydrostatic piezoelectric coefficient dh for single domain crystals was calculated to be ∼55 pC/N, coincident with the experimentally determined values under hydrostatic pressure. For <001> oriented fields, piezoelectric coefficients d33<001> and d31<001> as high as 2250 and -1000 pC/N were determined, respectively. Although a high value of dh<001> (∼250 pC/N) was expected, the experimentally determined value was only ∼50 pC/N. A change of polar vector within the crystal lattice was discussed in relation to the volume strain associated with an E-field induced phase transition and the possible origin of the discrepancy in hydrostatic dh values. © 1999 American Institute of Physics.