Molecular motion and relaxation studies using a thermal windowing thermally stimulated depolarization current (TW-TSDC) were performed for aliphatic polyureas 7 and 9. Global thermally stimulated depolarization current gave three characteristic major peaks corresponding to the alpha, beta, and gamma relaxation modes at 78.5, -44, and -136 degrees C for polyurea 7 and at 80, -50, and -134 degrees C for polyurea 9, respectively. The a:relaxation is related to the large-scale molecular motion due to microBrownian motion of long-range segments. This relaxation is significantly related to the glass-transition temperature. The beta relaxation is caused by the local thermal motion of long-chain segments. The gamma relaxation is caused by the limited local motion of hydrocarbon sections. Temperature dependence of relaxation times was expressed well using Vogel-Tammann-Fulcher (VTF) expression. 3-D simulation of dielectric constants of dielectric strength and lass factor were performed in the frequency range from 10(-6) to 10(4) Hz and temperature range from -150 to 250 degrees C, using the relaxation parameters obtained from the TW-TSDC method.