The U.S. Environmental Protection Agency (EPA) established the Center for Water Quality Modeling to provide a focal point for water quality modeling activities. The Center supports a range of techniques and computer programs for water quality analysis ranging from simple desk-top techniques appropriate for preliminary analysis to sophisticated continuous simulation models for detailed planning. This paper describes the models supported by the Center and gives an overview of the Center's activities, which include distribution and maintenance of computer programs, training, and sponsorship of a users group.