A composition dynamics model is developed for un-agitated perforated plate liquid-liquid extraction columns. The linearization of the phase equilibrium relation enabled the analytical solution of the set of differential difference equations describing the dynamics of the compositions of each of the continuous and dispersed phases on any plate within the column. The system dynamic parameters are expressed in terms of the dead times and mixing lags associated with the flow of the two phases in the active contact area and in between the plates. Frequency response data have been generated to elucidate the effect of total number of plates, plate spacing, phase flow rates, and the slope of the linearized equilibrium curve on the obtained system dynamics. The rather involved transfer functions describing the extract and raffinate product composition dynamics have been approximated to simple transfer functions involving a dead time and a first order lag which are functions of the relevant design, operating, and physico-chemical parameters. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.