To uncover lessons from past experiences that may help guide future counterterrorist efforts, this report presents an overview and evaluation of the major antiterrorist measures that have been used and considered by the United States. Those measures have included the implementation of physical security at domestic and foreign facilities, and intelligence gathering and analysis. The author identifies several lessons that can be learned from U.S. include the critical role that intelligence plays in counterterrorist efforts, the difficulty in designing a consistent political and military strategy to combat such a diverse threat as terrorism, and the need to eliminate excessive statements and promises about counterterrorist action since the terrorist threat can never be completely eliminated.