The Longitudinal Study of Generations (LSOG), initiated in 1971, began as a survey of intergenerational relations among 300 three-generation California families: grandparents (then in their sixties), middle-aged parents (then in their early forties), and grandchildren (then aged 15 to 26). The study broadened in 1991 and now includes a fourth generation, the great-grandchildren of these same families. The LSOG, with a fully elaborated generation-sequential design, allows comparisons of sets of aging parents and children at the same stage of life but during different historical periods. These comparisons make possible the investigation of the effects of social change on inter-generational solidarity or conflict across 35 years and four generations, as well as effects of social change on the ability of families to buffer stressful life transitions (aging, divorce and remarriage, higher female labor force participation, changes in work and the economy, and possible weakening of family norms of obligation), and the effects of social change on the transmission of values, resources, and behaviors across generations. The study also examines how intergenerational relationships influence individuals' well-being as they transition across the life course from early, to middle, to late adulthood. The LSOG contains information on family structure, household composition, affectual solidarity and conflict, values, attitudes, behaviors, role importance, marital relationships, health and fitness, mental health and well-being, caregiving, leisure activities, and life events and concerns. Demographic variables include age, sex, income, employment status, marital status, socioeconomic history, education, religion, ethnicity, and military service.