Abstract: The effect of a rank deficiency upon curve resolution in simple kinetic reaction-based systems is studied. Firstly, simulated rank-deficient spectrophotometric data of a mixture of two reagents, each one yielding its own reaction product by a first-order kinetic reaction, are analyzed. Four different situations are considered according to the differences in the spectral responses of the reaction constituents and to the differences in the rate constants between the two kinetic processes. A variation of the rate constant between runs for a certain kinetic process is also taken into account. Secondly, the resolution of a real rank-deficient data system, corresponding to the study of the pH-dependent decomposition of 1,2-naphthoquinone-4-sulfonate, is investigated. All these studies were carried out using a multivariate curve resolution method based on the alternating least squares optimization of the kinetic and spectral profiles of the species present in the system.