The Clean Water State Revolving Fund (CWSRF) was created in 1987 by Congress with the intent of providing states with a continuous source of funding to address water quality projects. Since its inception, this unique col-laboration between EPA and the states has grown to become the largest federal funding program for water infrastructure projects across the country. This 2005 Annual Report on the Clean Water State Revolving Fund provides an overview of the activities, accomplishments, and future plans for this highly successful program. Over the past 18 years, state CWSRF programs have loaned $52.7 billion for projects to maintain and improve publicly owned treatment works, mitigate non-point source pollution, and promote estuary management. The CWSRF continues to serve as a cost-effective water infrastructure financing mechanism.