The poling effect on the [011]-oriented (1 - x) Pb(Mg1/3Nb2/3) O-3-xPbTiO(3) (PMN-xPT) single crystals across the morphotropic phase boundary (MPB) was studied. The dielectric and piezoelectric properties were investigated as a function of the poling field. Domain structure evolutions during the poling process were recorded. In the unpoled PMN-xPT phase diagram, an apparent rhombohedral (R)-tetragonal (T) phase boundary exists. With room-temperature poling, the structure transformation sequence strongly depends on the composition. The crystal experiences a direct transition to the 2R/2T domain state in the rhombohedral or tetragonal phase field beyond the MPB region, whereas within the MPB zone it is hard to achieve the 2R/2T engineered configuration although the initial state is either rhombohedral or tetragonal as well. The piezoelectric responses of the MPB center dot PMN-xPTs are extraordinary weak (d(33) similar to 250 pC/N), in contrast to the [011]-oriented multidomain PMN-xPTs with ultrahigh-piezoelectric coefficient (d(33) > 1000 pC/N). We demonstrate that a slight composition variation near the MPB will significantly influence the domain evolution route and piezoelectricity for the [011]-oriented PMN-xPT crystals. We also confirm the feasibility to realize the 2R/2T engineered domain configuration for the [011]-oriented MPB crystals, which will extend the desired portion of the Bridgeman-grown boules with optimal piezoelectric properties.