Ethyl methacrylate, ethylene glycol dimethacrylate free radical crosslinking co-polymerization reaction is studied by dielectric spectroscopy at various temperatures. A maximum in the dielectric constant was observed during the gelation reaction. At the same point, the dielectric loss switched from a linear decrease to a relatively constant behavior. Parallel experiments, performed with a magnetic stirrer, showed that this maximum is consistent with the gel-point. In the ethyl methacrylate homopolymerization reactions the dielectric constant did not go through a maximum but decreased monotonically. The evolution of the dielectric constant is found to depend on the extent of the reaction, but not on time and temperature separately. (C) 2002 Elsevier Science B.V. All rights reserved.