This paper proposes a graphical design method for quaternary systems in simultaneous chemical and physical liquid-liquid equilibrium (reaction-separation process). The reactive phase equilibrium data and the stage by stage calculation are represented into two projections diagrams with rectangular coordinates. The graphical method has been applied to reversible reactive systems where all of the components of the reaction have the same stoichiometric coefficient. This graphical method allows estimating the number of reactive theoretical stages, the limits of the solvent to feed ratio (DIP), the extent of reaction and the conversion. Results obtained for seven design problems (involving four different reactive systems) are in good agreement with state of the art simulation software and with literature. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.