In this study, the effect of water addition on cure kinetics in an epoxy-amine thermoset was investigated. Near FTIR spectra demonstrated that a small amount of water addition significantly accelerated the cure reaction in terms of epoxide conversion, with water acting as a catalyst for the reaction. Use of a modified mechanistic model allowed direct comparison of the effect of hydroxyl groups generated from water addition to those generated from the polymer chain. The comparison of those kinetic parameters shows that the two effects are very close, in which difference in the logarithmic value of the reaction constant is less than one order of magnitude over all the reaction conditions. The kinetic study also confirmed a strong negative substitution effect for this system. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4650-4659, 2011