This chapter sets out the main goal of the volume: to examine the role of education in shaping rates and patterns of intergenerational social mobility among men and women during the twentieth century. This is a particularly timely question given the concerns of politicians and policy makers with intergenerational mobility and their belief that the solution lies in education. The chapter explains what we mean by social mobility and the distinction between absolute and relative mobility, and it sets out the reasons why we expect changes to the educational system to lead to changes in both absolute and relative mobility. The chapter discusses the reasons for choosing the eight countries on which we focus: the United States, Sweden, Germany, France, the Netherlands, Italy, Spain, and Switzerland. The operationalization of our main variables is explained and the questions to be addressed in each of the subsequent country chapters are set out.