Since they began in 1955, the Duke Longitudinal Studies have aging have been regarded as landmark investigations, amassing invaluable data on the typical physical changes that accompany aging, typical patterns of mental health and mental illness, psychological aging, and the normal social roles, self-concepts, satisfactions, and adjustments to retirement of the aged. Comprising information on more than 750 aged and middle-aged persons, these studies have contributed enormously to our ability to distinguish normal and inevitable processes of aging from those that may accompany aging because of accident, stress, maladjustment, or disuse.