Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) ferroelectric single crystals with rhombohedral symmetry demonstrate a wide variety of anisotropic behavior under both unipolar and bipolar electrical switching. Specifically, PZN-4.5%PT crystals demonstrate exceptional polarization switching fatigue resistance along C (C: pseudocubic), as opposed to normal fatigue in C directions in the rhombohedral ferroelectric state [Takemura etal, J. Appl. Phys. 88, 7272 (2000)]. The influence of prior exposure to electrical cycling on polarization switching as a function of electric field and driving frequency was studied in both orientations. The field and frequency dependence of switching polarization can be described by a power law, in which greater electrical field strength and frequency dependence are shown for C crystals. As fatigue evolves in the C orientation, higher electric fields are required for switching due to the changes in microscopic switching mechanisms and buildup of local internal electric fields. However, negligible changes are observed in C-oriented crystals as a function of cycling. These differences are consistent with switching current and strain-field analyses. From strain-field data, asymmetry can be detected in bipolar strain loops accompanying the suppression of the polarization-electric-field switching. The asymmetry is localized, as noted by region-to-region changes in strain-field loops across the surface of the C PZN-PT crystals. © 2004 American Institute of Physics.