This study proposes to examine the generational factors that affect social changes in attitudes, opinions, and values. Policy makers and social observers often assume that social change within the larger society necessarily stems from changes in the values, attitudes and opinions of individuals. But there is another possibility: change could stem from cohort replacement, that is, the replacement of older birth cohorts (for example, those born in the 1890s) with later ones (for example, those born in the 1960s). In fact, there are good reasons to believe that cohort replacement has been an important source of recent change in U.S. public opinion on such diverse issues as racial segregation, the proper roles for women, and whether or not government officials can be trusted. Yet that possibility has not been systematically examined. In an attempt to determine cohort replacement's contribution to recent social change in the U.S., this research uses annual and bicennial survey data on social and political attitudes in the U.S. collected over the last 25-30 years. A wide span of important and controversial issues will be examined, including political attitudes, religious beliefs and practices, neighborhood, and so on), attitudes about abortion, and attitudes about women's roles. The results will be useful to policymakers as well as to social scientists, because knowledge about cohort replacement effects can help us determine the likely direction of future social change. For example, if opposition to school integration is found predominantly among the older cohorts, then that opposition should subside as those cohorts die off.