The Duke Longitudinal Studies of Aging were preceded by a research project supported by the National Institutes of Health and entitled "The Effects of Aging upon the Central Nervous System: A Physiological and Psychological Approach." These earlier studies formed a solid basis for designing and carrying out the two Duke Longitudinal Studies. The Duke longitudinal interdisciplinary research team existed between 1955 and 1980. The first longitudinal study of "normal aging" began in 1955. The subjects were 270 community residents and volunteers aged 60 to 90. Eleven rounds of complete examinations were carried out. The eleventh and final round occurred in 1976. The second Duke Longitudinal Study (also known as the "Adaptation Study") began in 1968 and ended in 1976. The research design was cross-sequential with 502 subjects 46 to 70 years of age. Numerous ancillary studies were conducted on both studies. Both studies included biomedical, psychological, and socioeconomic observations and evaluation procedures. All data are preserved and available for secondary analysis by qualified persons.