This report presents the RAND study that resulted from a request to assist the Secretary of Defense in drafting an Executive Order to end discrimination on the basis of sexual orientation in the U.S. Armed Forces. Taking an interdisciplinary approach, a team of RAND researchers visited seven foreign countries and the police and fire departments in six American cities, seeking insights and lessons from analogous experiences there. The team considered the integration of blacks and the development of the current policy that prohibits homosexuals from serving in the military. It reviewed public opinion, including the views of current active-duty military personnel, and the scientific literature on group cohesion, sexuality, and related health issues. It examined a number of legal and enforcement issues, as well as the literature that deals with implementing change in large organizations. Based on the research findings, the study group found that the most promising policy option for achieving the President's objectives focuses on conduct and considers sexual orientation, by itself, as not germane in determining who may serve in the Armed Forces. As part of the study an illustrative "Standard of Professional Conduct" was also designed with the overarching objective of maintaining the order and discipline essential for an effective military organization. The report also notes that if sexual orientation is regarded as not germane in determining who may serve in the military, it is equally not relevant to decisions on assignment, pay, military sociality, and benefits. The manner in which such a policy change is implemented could have a decisive impact on the acceptance of the new policy by the military. Based upon the research conducted in this study, key elements of an implementation strategy were identified: (1) the message of policy change must be clear and must be consistently communicated from the top; (2) the option selected should be implemented immediately; (3) emphasis should be placed on behavior and conduct, not on teaching tolerance or sensitivity; (4) leadership must send messages of reassurance to the force; (5) leaders at all levels should be empowered to implement the policy, with special training provided if necessary; and (6) a monitoring process should be established to identify problems early in the process and to address them immediately. The option presented in this report appears to meet the President's criteria, and is consistent with the empirical research and historical experience. By following the implementation strategy, the Department of Defense should be able to increase the probability that a policy that ends discrimination based on sexual orientation can be implemented in a practical and realistic manner.