To be selected for a position of such trust and responsibility, one must be granted a security clearance. The clearance process, which is strictly governed by rules and regulations derived from Federal statute and executive orders, begins when you accept a conditional offer of employment from the Agency. It entails a thorough examination of your life history and fitness to safeguard the nation's secrets. Think of this process as the first step in building a bridge of trust between you and the Agency. Candor is an essential ingredient in the establishment of that trust. (emphasis added)

The investigation addresses comprehensively one's loyalty to the United States, strength of character, trustworthiness, honesty, reliability, discretion, and soundness of judgment. In addition it examines one's freedom from conflicting allegiances, potential for coercion, and willingness and ability to abide by regulations governing the use, handling and protection of sensitive information.

The Agency uses the polygraph to check the veracity of information which bears upon the areas listed above. CIA's polygraph examiners  are highly trained security professionals, among the world's best in their field. They work closely and carefully with applicants to ensure that  the information upon which clearance decisions are based is as accurate as it can be and is guarded with the strictest confidence.