The basic issue underlying this research is whether or not adult personality structures change after maturity is reached. Problems involved in the longitudinal study of psychological variables are discussed and 2 feasible designs applied in an effort to differentiate the effects of chronological age, secular trends, generation differences, as well as the effects of repeated measurement upon selected personality variables for adults ranging in mean age from 25-81 years. The first involves performance-task measures of personality style, psychomotor speed and motor-cognitive rigidity, while the second involves questionnaire responses concerning personality traits, personality-perceptual rigidity and social responsibility. All measures show significant age differences which are interpreted as generational differences. While the data is consistent with a stability model of adult personality, many interesting phenomena are suggested for the developmentalist. The author concludes that, although adult personality structure doesn't change, the sociocultural impact upon successive generations leads to clearly observable age differences in personality at any single historical point. (Author/TL)