The recent explosion in population aging across the globe represents one of the most remarkable demographic changes in human history. There is much concern about population aging and its consequences for nations, for governments, and for individuals. It has often been noted that population aging will inevitably affect the economic stability of most countries and the policies of most state governments. What is less obvious, but equally important, is that population aging will profoundly affect families. Who will care for the growing numbers of tomorrow's very old members of societies? Will it be state governments? The aged themselves? Their families? The purpose of this volume is to examine consequences of global aging for families and intergenerational support, and for nations as they plan for the future. Four remarkable social changes during the past fifty years are highlighted: (1) Extension of the life course: A generation has been added to the average span of life over the past century; (2) Changes in the age structures of nations: Most nations today have many more elders, and many fewer children, than fifty years ago; (3) Changes in family structures and relationships: Some of these differences are the result of trends in family structure, notably higher divorce rates and the higher incidence of childbearing to single parents; (4) Changes in governmental responsibilities: In the last decade, governmental responsibility appears to have slowed or reversed as states reduce welfare expenditures. How will families respond to twenty-first-century problems associated with population aging? Will families indeed be important in the twenty-first century, or will kinship and the obligations across generations become increasingly irrelevant, replaced by "personal communities"? This volume goes a considerable distance to answer these critical issues for the twenty-first century. Vern L. Bengtson is an AARP/University Chair in Gerontology and Professor of Sociology, University of Southern California. Ariela Lowenstein is associate professor and head, Department of Aging Studies, University of Haifa, Israel.