Pb(Mg1/3Nb2/3)O-3-35 mol% PbTiO3 (PMN-35PT) specimens with a 5 mol% excess PbO were prepared by excessive heat treatment at 1150degreesC to induce abnormal grain growth. Through electron backscatter diffraction analysis and the observation of a three-dimensional morphology, the abnormally grown PMN-35PT grains were found to be twinned crystals with penetration characteristics. The morphology of the PMN-35PT twinned crystal was crystallographically analyzed. The abnormal grain growth of PMN-35PT is suggested to be due to preferential growth at the reentrant angles formed by twins.