Polymerization kinetics of tri-ethylene glycol dimethacrylate (TrEGDMA)/2,2-azobis-isobutyronitrile (AIBN) mixtures (0.1% w.t.) at different temperatures was investigated by using dielectric relaxation spectroscopy. The dielectric spectra at the polymerization temperatures studied are dominated by high conductivity leading us to employ the electric modulus representation in order to extract information about the evolution of the system during isothermal reaction. An intense peak appears in the imaginary component of the complex dielectric modulus which is related to conductivity. The variation of the strength of this peak and of its relaxation time with the polymerization time allows us to determine the polymerization degree evolution and the moment in which vitrification is attained, which can be compared with results obtained by temperature modulated DSC in a previous work (Viciosa MT, Hoyo JQ Dionisio M, Gomez Ribelles JL Journal of Thermal Analysis and Calorimetry 2007; 90:407-414). The study was completed with a detailed analysis of conductivity carried out in the unreacted system using both dielectric modulus and conductivity representations. (C) 2011 Elsevier Ltd. All rights reserved.