This Article concerns the duty of care in American corporate law. To fully understand that duty, it is necessary to distinguish between roles, functions, standards of conduct, and standards of review. A role consists of an organized and socially recognized pattern of activity in which individuals regularly engage. In organizations, roles take the form of positions, such as the position of the director. A function consists of an activity that an actor is expected to engage in by virtue of his role or position. A standard of conduct states the way in which an actor should play a role, act in his position, or conduct his functions. A standard of review states the test that a court should apply when it reviews an actor’s conduct to determine whether to impose liability, grant injunctive relief, or determine the validity of his actions. In many or most areas of law, standards of conduct and standards of review tend to be conflated. For example, the standard of conduct that governs automobile drivers is that they should drive carefully, and the standard of review in a liability claim against a driver is whether he drove carefully. Similarly, the standard of conduct that governs an agent who engages in a transaction with his principal is that the agent must deal fairly, and the standard of review in a claim by the principal against an agent, based on such a transaction, is whether the agent dealt fairly. The conflation of standards of conduct and standards of review is so common that it is easy to overlook the fact that whether the two kinds of standards are or should be identical in any given area is a matter of prudential judgment. In a corporate world in which information was perfect, the risk of liability for assuming a given corporate role was always commensurate with the incentives for assuming the role, and institutional considerations never required deference to a corporate organ, the standards of conduct and review in corporate law might be identical. In the real world, however, these conditions seldom hold, and in American corporate law the standards of review pervasively diverge from the standards of conduct. Traditionally, the two major areas of American corporate law that involved standards of conduct and review have been the duty of care and the duty of loyalty. The duty of loyalty concerns the standards of conduct and review applicable to a director or officer who takes action, or fails to act, in a matter that does involve his own self-interest. The duty of care concerns the standards of conduct and review applicable to a director or officer who takes action, or fails to act, in a matter that does not involve his own self-interest.