The anisotropic fracture behavior in unpoled and poled (1-X)Pb(Zn2/3Nb1/3)-xPbTiO(3) (x=0.045) (PZN-4.5%PT) single-crystal relaxor ferroelectrics cut along the crystal planes, [010] and [001], was characterized. The crack tip toughness (K-tip) determined from Vickers indentations was compared with the R-curve behavior measured using the single-edge V-notch beam (SEVNB) method. Several of the SEVNB fracture experiments resulted in cracks forming and propagating under mixed mode loading (K-I and K-II) along the [110] crystal plane. Other specimens formed cracks at 0 degrees along the [010] plane. To assess the anisotropic fracture behavior, the local and global critical energy release rates were determined using Stroh's formalism.