The ferroelectric behavior and structural change induced by the external electric field were observed for poly(trimethylene terephthalate) (PTT), which has nonpolar crystalline structure with carbonyl groups aligned antiparallel to each other. The displacement-electric field hysteresis curves of PTT films showed hysteresis above 140 degrees C, which indicated the polarization reversal of PTT. The pyroelectric constant and thermally stimulated depolarization current suggest the depolarization of the polar structure of PTT induced by the external electric field above 150 degrees C. An endothermic peak caused by the depolarization was also observed in the differential scanning calorimetry for the PTT film poled at 30 MV/m. The change of the crystalline structure and the orientation of carbonyl groups induced by the electric filed were investigated by X-ray diffraction patterns and infrared spectra. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1991-1996, 2009