Electronic surveillance by the US Government and the corresponding implications for privacy protection have come under increased public scrutiny after the terrorist attacks of September 11, 2001. The USA PATRIOT Act, passed in response to the attacks and containing sweeping changes in this area, has alarmed many civil liberties groups. This article examines the nature of these changes in light of increased concerns over national security, and attempts to articulate the arguments advanced by both the US Government and privacy advocates with respect to the need and appropriateness of the legal response to the growing threat of terrorism.