The dielectric behaviour of isocyanate-terminated polymers is reported in this paper as a function of frequency (100 Hz-100 kHz), temperature (30-90 degrees C) and the concentration of the curing agent, 4,4'-methylene bis(ortho-chloroaniline) (MOCA) (1.2, 3.5 and 4.7%) which was used in preparing the polymer from the toluene di-isocyanate and castor oil. The dielectric constant and the loss were found to decrease as the MOCA concentration was increased. Distinct loss peaks were obtained. The influence of the curing agent on the dielectric properties of the polymer is discussed in detail. The most probable relaxation times were calculated from the complex arc plots of epsilon 'and epsilon ". From these arc plots it is established that the distribution of relaxation times becomes more and more symmetric with the increasing temperature. Activation energies were calculated. Maxwell-Wagner-Sillars interfacial polarisation is proposed as the probable mechanism.