The aim of this work is to describe the ingress of ionic species into a saturated porous medium. The paper focuses on the case of cement-based materials penetrated by chloride. A new approach is proposed to describe ionic transfer in porous media. This approach is based on the Nernst-Planck equation rather than Fick's laws, in order to account for the interactions of the different ions in the bulk solution. It is shown that this method can be applied to several fields of research, such as chloride decontamination and nuclear decontamination. Copyright (C) 2003 John Wiley Sons, Ltd.