The cure behavior of unsaturated polyester(UP)/organo-montmorillonite (Org-MMT)/methyl ethyl ketone perokide (MEKP)/cobalt octoate intercalated nanocomposites at varying temperatures and Org-MMT loadings was investigated by the Dynamic Torsional Vibration Method (DTVM). The apparent kinetic parameters of the cure reaction, including the gelation time t(g), apparent activation energy E-a, and curing rate, etc., were estimated by Flory's elation theory, non-equilibrium thermodynamic fluctuation theory, and Avrami equation. The theoretical prediction is in good agreement with the experimental results obtained by the DTVM. The gelation time t(g) increases, and the rate of curing reaction decreases, with 9 increasing Org-MMT loadings, but there is no obvious effect of Org-MMT on the apparent activation energy E, and the curing process of nanocomposites. A two-step cure process of UP was observed due to the addition of Org-MMT. © 2005 Wiley Periodicals, Inc.