Editors' Summary: The Clean Water Act is undergoing a dramatic shift toward water quality-based regulation. Leading the charge, and taking their share of opposing fire, are the long-dormant provisions of §303(d) calling for the development of total maximum daily loads (TMDLs) for impaired waters. Earlier Articles in this series described the legislative and regulatory history of TMDLs, the litigation surrounding them, and the Administration's current efforts to redesign the program. This final Article attempts to step back and assess the potential of the TMDL program. It concludes that, while TMDLs are a highly resource-intensive and indirect way to approach the significant remaining water pollution problems of this country, they hold the promise of progress with sufficient time and money, more active state leadership, and the retention of elements that have proven key to the success of the Act's point source discharge program as well: numerical targets, fixed plans, and the ability of people concerned about clean water to ensure that they are met.