During pharmaceutical syntheses, the reaction solvent has often to be switched off from one reaction step to the following one. Because of the standard industrial practices, solvent replacement generally constitutes a slow and high solvent-consuming operation. In this paper, a specific methodology, based on an optimisation framework dedicated to batch processes, is proposed for the optimisation of solvent replacement procedures. Optimisation may be performed at different levels according to economic and environmental criteria and satisfying safety and waste treatment constraints. In this way, the proposed methodology allows both to design new procedures of solvent replacement and to improve existing industrial processes. Two industrial applications are detailed to emphasize the benefits related to this methodology. In each case, the proposed methodology leads to the suitable recipe from comparison of traditional and empirical replacement procedures generally used in the pharmaceutical industry. (c) 2006 Elsevier B.V. All rights reserved.