Error in medicine is common and can lead to significant patient injury. Although successful systematic efforts to reduce human error have been applied in other complex systems, the field of medicine has just begun to make a broad-based effort in this regard. However, both research in and implementation of patient safety measures may not occur without considering important legal issues that may impede these health policy efforts. Tort and contract law may interact with the vagaries of managed care to limit participation in these error reduction efforts by health care providers as well as by managed care organizations. Thus, for patient safety research to be successful, all members of the health care enterprise must participate in a coordinated effort to identify and establish effective practices that may reduce human error in medicine. But beyond this understanding, it is imperative that legal impediments be recognized and addressed before the goal of a continuously improving, increasingly safe health care system can become a reality.