In epoxy-amine kinetic studies, the determination of the ratio of rate constants (R) for hydrogens on primary and secondary amine groups is very important; in fact R is related to the network morphology. In this paper we show that R can be directly calculated from the ratio of the concentrations of primary to secondary amine at (d[A(2)]/dt)(max), d[A(2)]/dt being the reaction rate for the formation of the secondary amine. Experimental measurements were carried out in the near infrared.