In June 2005, the RAND Corporation and the Office of the Director of National Intelligence convened a one-day workshop to discuss how theories underlie intelligence and might lead to both a better understanding and better practice of U.S. intelligence. Forty attendees (practitioners, academics, and specialists) participated in four panels: What Is Intelligence Theory?; Is There an American Theory of Intelligence?; Which Assumptions Should Be Overturned?; and How Can Intelligence Results Be Measured? Issues debated included whether intelligence should be defined narrowly, as secret state activity, or broadly, as information for decisionmaking; whether there is a uniquely American theory or practice of intelligence, in its technology, militarization and congressional oversight; whether closer relationships between intelligence officers and policymakers leads to politicization; and how to devise metrics for assessing the performance of intelligence. Readers will find opinions that look familiar as well as others that challenge or refine the customary formulations.