The Superfund program is one of the U.S. Environmental Protection Agency's (EPA) most controversial and most visible programs. Yet, defining success for Superfund has been extremely difficult. When the program-formally known as the Comprehensive Environmental Response, Compensation, and Liability Act, or CERCLA-first began in the early 1980s, EPA set as its major goal deleting sites from the National Priorities List (NPL). Sites listed on the NPL are generally considered the most contaminated in the nation, and EPA funds can be spent on long-term cleanups only at these sites. In order for a site or portion of a site to be deleted from the NPL, all response actions must be complete and all cleanup goals must be achieved; in other words, the site must require no additional cleanup activities.