The model of transient multicomponent mass transfer in a Q-cascade is developed, It enables to study the physical regularities of alteration of concentrations along the cascade stages and in the product flow from the cascade. The capability of the developed model is demonstrated by calculation of the transient process and the time-to-steady-state in a gas centrifuge cascade for separation of krypton isotopes. (C) 2015 Elsevier Ltd. All rights reserved.