Transient kinetics of a three-step reaction mechanism is analyzed in detail by means of computer simulation. Step increase of inlet reactant concentration, under isothermal conditions, is employed as a perturbation. Analysis is based on the transient responses of the rates of elementary steps. Four types of transient kinetic behaviour were found. The general nature of non-stationary behaviour of a set of consecutive steps is revealed from them. implications for the kinetic interpretation of measurable transient responses are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.