The property degradation observed in thin Pb(Mg 1/3Nb 2/3)O 3-PbTiO 3 (PMN-PT) crystals is believed to relate to large domains and subsequent clamping induced by the surface boundary. In this work, the properties were investigated as function of domain size, using controlled poling. The degraded piezoelectric and dielectric properties of thin PMN-PT were found to increase significantly with decreasing domain size. Furthermore, the fine domain structure was found to be stable at 3 kV cm -1 after 7.0 × 10 5 negative-pulse cycles. These properties make PMN-PT crystals suitable for high-frequency (>20 MHz) ultrasound transducers. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.