Issues examined were the extent to which the European Command's antiterrorism strategy encompasses in-transit forces at seaports in its area of responsibility, whether there is an oversight mechanism that reviews and evaluates the antiterrorism approach for in-transit forces at seaports, and whether there are significant challenges in the implementation of antiterrorism measures at seaports used by the European Command. As part of this evaluation, researchers examined antiterrorism efforts at three seaports -- one in Italy and two in Spain -- within the European Command's area of responsibility. The evaluation was conducted from July 2002 through June 2003 in accordance with generally accepted government auditing standards. The evaluation found that the European Command's antiterrorism approach is designed to protect most in-transit forces at seaports; however, there are two potential gaps in the strategy that may leave some vessels more vulnerable to terrorist attacks. The strategy is based on individual ship in-port security plans that must be approved by the Navy prior to a ship's entering a port and on the use of more secure seaports. One vulnerability of this approach is that some vessels chartered by the U.S. Department of Defense (DOD) to transport equipment have not been required to submit in-port security plans before port visits. Another security vulnerability is that operational requirements preclude the exclusive use of more secure ports even when increased security is necessary. The study also found that there are no oversight mechanisms to evaluate the European Command's overall approach or specific antiterrorism measures for in-transit forces; gaps or weaknesses, therefore, may not be identified. The evaluation identified two challenges in the implementation of antiterrorism measures at European Command seaports. First, variations in host national support affects DOD's ability to fully implement its antiterrorism measures. Second, weaknesses related to the crew-screening process for chartered vessels could jeopardize the safety and security of crews, vessels, and cargo, as well as the ports they visit. The evaluation recommends that DOD improve in-transit antiterrorism efforts by clarifying antiterrorism responsibilities, periodically reviewing antiterrorism measures, strengthening crew screening, and establishing a new port security measure. DOD generally agreed with the recommendations in the report. 2 tables, 1 figure, and appended scope and methodology