Reuse of industrial wastewater is an important strategy for reducing freshwaterconsumption and wastewater generation. This paper outlines a methodology forassessing the economic performance of industrial wastewater reuse systems thatinvolve water upgrading. From an economic perspective, wastewater reuse reduces the costsof freshwater supply and wastewater disposal. Reusing signicant quantities of wastewatertypically involves regeneration=treatment of the available wastewater to meet the higher waterquality requirements of water-using activities. However, the cost of wastewater regeneration=treatment rises exponentially with increasing contaminant removal effciency. This paperdemonstrates the importance of balancing these competing cost factors (freshwater andwastewater disposal costs vs wastewater regeneration=treatment cost), which are functions ofthe post-regeneration=post-treatment contaminant concentration. The proposed cost optimizationprocedure can be used to minimize the total cost of a wastewater reuse system with eitherwastewater regeneration reuse or wastewater treatment reuse.