In a rapidly changing world, the success of nations, communities, and individuals may be linked, more than ever before, to how they adapt to change, learn, and share knowledge. This report helps clarify the concepts of human and social capital and evaluates their impact on economic growth and well being. Although the evidence on social capital is less developed, reflecting the novelty of the concept in economic and social science, the report draws on a number of empirical studies which suggest potentially important correlations between human and social capital. The evidence suggests that human and social capital can be of key importance in contributing to a wide range of positive outcomes, including higher income, life satisfaction, and social cohesion. Although there is no evidence for systematic "under-investment" in either human or social capital, concerns are expressed about the distribution and quality of each form of capital and how this might impact future well being. This report finds that there is limited scope for public policy to change the quality, stock, and distribution of human and social capital in the short term. However, a number of areas are discussed in which public, private, and voluntary actors may leverage long-term improvements in both human and social capital. Appendices are: "Some Measures of Well-being"; "Some Trends in the Social and Economic Environments"; "Determinants of School Attainment: The Research Evidence"; "The Impact of Human Capital on Economic Growth: Some Major Studies"; and "Are Trust and Civic Engagement Declining in OECD Countries?" (Contains 13 pages of references.) (BT)