Data supporting the notion of adult personality stability are challenged by the present findings, in which developmental change was demonstrated using the Eriksonian-stage-based Inventory of Psychosocial Development (IPD; Constantinople, 1969). A sequential design over the ages 20-42 was used on 2 cohorts of college students and alumni originally tested in 1966 and 1976-1977 (ns in 1988 = 99 and 83, respectively), and a 3rd cohort of college students in 1988-1989 (n = 292). Results of longitudinal, cross-sectional, and sequential analyses challenged ideas about personality stability, with evidence of increasingly favorable resolutions of the early Eriksonian psychosocial stages up through the oldest age studied. There was evidence of a trend over the past decade toward less favorable resolution of ego integrity versus despair. The findings were interpreted in terms of developmental change processes during the adult years interacting with culturally based environmental effects on psychosocial development.