ReDrop is a simulation tool which can predict the behaviour of pulsed extraction columns on pilot-plant scale. Because it follows a certain number of drops during their entire lifetime in an extraction column, it can be seen as a Monte-Carlo solution of drop-population balances. Re Drop is based on single-drop models which have system-specific parameters. These parameters are determined from lab-scale experiments with single drops. In this study, Re Drop is extended to RDC extraction columns and simulations are carried out for the standard test systems toluene (d) + water (c) + acetone (c -> d) and n-butyl acetate (d) + water (c). The calculated hold-up and Sauter mean diameter show good agreement with the experimental data obtained in pilot-plant scale experiments. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.