This paper explores the relationship between age and individual differences. Two hypotheses were tested through the use of repeated measures of functioning in terms of social, psychological, and physiological parameters: (1) individual differences do not decrease with age, and (2) individuals tend to maintain the same rank in relation to age peers throughout the later years of life. Data is taken from an ongoing eighteen-year longitudinal investigation of human functioning. The sample is composed of 106 survivors of an original panel of 271 persons initially 60 years or older. Conclusions are as follows: (1) when the mortality and dropout of a sample are controlled, the variances of a number of social, psychological, and physiological factors tend to remain constant through time; and (3) the range of observed individual differences is maintained, and within that range individual's rank ordering is relatively constant. (Author/LKP)