The study is based on data derived from the Rand Chronology of International Terrorism, a review of current literature on terrorism counteraction, and an examination of selected military countermeasure programs. Analyses of terrorist targeting indicate an apparent increase in premeditated attacks against U.S. military installations and personnel. The services have responded by spending over $2 billion annually for physical security alone. An analysis of antiterrorism (AT) and counterterrorism (CT) programs reveals four critical elements in effective AT or CT efforts. They are credible, reliable, and timely intelligence; proper education and training; modern tactics and techniques; and up-to-date equipment and devices. The problems of meeting the intelligence requirement have been compounded by the severe constraints imposed on U.S. intelligence agencies during the anti-Vietnam War era and also by an absence of communication between the intelligence community and those who need and use intelligence information. These problems may be relieved by a relaxation of some intelligence-gathering constraints and the assignment of operations personnel to an all-source information center. Education and training in CT are conducted primarily by the Army and the Air Force. The Navy and Marines generally use Army and Air Force training facilities or those of other government agencies. In addition to training for AT and CT< specialists, training should be provided for potential targets of terrorism, and terrorist tactics should be analyzed as the basis for devising CT measures. The barricade-and-hostage tactic has had the greatest impact on CT measures, leading to the creation of special CT rescue teams within all military branches. The military could make better use of state-of-the-art equipment available in the private sector, such as new communications equipment, ammunition and weapons, and night-vision equipment. The future holds the threat of increasing international, state-sponsored terrorism. This trend could be significantly countered by more cross-service AT and CT initiatives directed by the Defense Department. Each section is footnoted, and a 27-item bibliography is provided.