Following the attacks of September 11, 2001, the Environmental Protection Agency and other government agencies removed information from their websites that they feared could invite attacks on critical public and private infrastructure. Accordingly, the benefits and costs of environmental information disclosure programs have come under increasing scrutiny. This paper provides a framework for examining these benefits and costs, and illustrates the framework through three brief case studies of information disclosure programs: risk management planning, materials accounting, and the Sector Facility Indexing Program. The paper closes by using these three cases to outline what we know and still need to find out about information disclosure programs.