This paper presents a method for targeting the capital and total cost of a mass exchange network. This part of the paper considers stagewise systems and uses a simplified capital cost correlation in order to convey the fundamentals. The method starts by determining the number of stages required, using the y - x composite curve plot presented previously, and then converts this to a capital cost. This target is combined with utility targets to give a target for the total annual cost. Simple design guidelines are presented, which allow these targets to be approached to within a few percent. The method is applied to a coke-oven gas sweetening example, which is a case involving two mass separating agents (MSAs) which do not overlap. It is also applied to an example involving phenol removal, in which there are overlapping MSAs. A final example deals with multicomponent transfer by extending the coke;oven gas problem. The paper introduces a new graphical tool, the y -y* composite curve plot, for handling systems with overlapping MSAs. The paper demonstrates that, contrary to previous belief. using the minimum number of units does not necessarily lead to a minimum cost design.