Since the inception of the NPDES stormwater program in 1990, municipal permittees have largely focused on new or redevelopment efforts to meet post-construction regulatory requirements. As successful as these efforts have been, they have not historically addressed the impact of existing development, especially in older, densely urbanized areas where the perceived cost of infrastructure replacement is high. Times, however, are changing, as attention to TMDL compliance and expanded Phase II coverage result in updated permit language and evolving stormwater management strategies. Additionally, advancements in stormwater treatment technologies such as high-rate biofiltration and versatile underground detention structures have reduced the cost and footprint of traditional low impact development approaches, bringing the goals of municipal stormwater infrastructure retrofit within reach. This presentation focusses on current methods to meet progressive regulatory requirements through regional stormwater control measures—large, multi-use projects that emphasize coordination between different municipal departments and deliver optimized benefits accordingly. These retrofit projects require advanced planning and coordinated funding, but they result in high-visibility water quality improvements to existing development that inform and engage local communities. Available cost-benefit analyses from California have demonstrated that a regional approach to meeting TMDL restrictions can be favorable to distributed, small control measure installations, especially when considering long term operation and maintenance costs. Washington State Department of Ecology is highlighted as an agency that successfully combines aggressive permit requirements with grant-based funding mechanisms that support permittees, making these types of projects achievable. Case studies from both states which utilize emerging technologies and demonstrate inter-agency cooperation are examined, providing guidance to stormwater program managers around the country.