The effects of temperature, acid concentration, and reactant concentration on the rate of formation of difurfuryldiamines from the reactions of furfurylamine with formaldehyde and acetaldehyde were experimentally investigated. On the basis of the data from these experiments, a semimechanistic reaction model network was proposed and a mathematical model which describes the observed kinetic behavior was derived. Rate constants for the model reactions were found to depend exponentially both on the reciprocal of the absolute temperature and on the acid concentration. The mathematical model predicts concentration versus time profiles for reactants, intermediate, and product for the reaction of furfurylamine and acetaldehyde under the following conditions : 20 degrees C < temperature < 50 degrees C, 3 M < nominal acid concentration < 6 M, 1.17 M < [furfurylamine] < 1.2 M, and 0.303 M < [acetaldehyde] < 1.17 M. For the reaction of furfurylamine with formaldehyde the model is applicable for 30 degrees C < temperature < 50 degrees C, 3 M < nominal acid concentration < 6 M, [furfurylamine] = 1.17 M, and [formaldehyde] = 0.58 M.