The 9/11 attacks have drawn attention to the security of many institutions, facilities, and systems in the U.S., incl. the nation¿s water supply and water quality infrastructure. These systems have long been recognized as being potentially vulnerable to terrorist attacks of various types, including physical disruption, bioterrorism/chem. contamination, and cyber attack. Damage or destruction by terrorist attack could disrupt the delivery of vital human services in this country, threatening public health and the environment, or possibly causing loss of life. This report presents an overview of this large and diverse sector, describes security-related actions by the government and private sector since 9/11, and discusses additional policy issues and responses. Illus.