A long-term longitudinal study of stability and change throughout adulthood will be continued with a follow-up interview of some 89 surviving members of a group who have previously been interviewed in young adulthood, middle age, and young-old age, and who are now old-old. Three broad sets of questions will be addressed: (1) the transition between young-old and old-old age; (2) the precursors of stability and change across adulthood and their impact on psychological well-being in old-old age; and (3) individual differences in amount and direction of change in old age. Many research questions will be analyzed in six major domains: (a) intellectual functioning, (b) health (c) life satisfaction, (d) social relationships, (e) retrospective perceptions of past events, and (f) family relationships. Analysis will utilize causal structural equations: LISREL models specifying hypothesized relationhsips between observed and reportey behaviors through adulthood as they regress upon the end-point behaviors observed in old-old age. The research is designed to increase our understanding of the relationships between internal change or continuity and situational, environmentally-linked events throughout adulthood and their input on psychological well-being in advanced old age. There are implications for public policy, as well: a knowledge of important precursors of successful aging is crucial in the design of preventive intervention programs to optimize aging.