Inequality studies are a relatively recent addition to development discourse. This chapter discusses their trajectory from the early postwar years to the present. In particular, it examines the work of Simon Kuznets in the 1950s, his model of the inverted-U, and the influence of his work on recent studies. Well into the 1980s, inequality studies were marginalized by major development actors. Exceptions to this neglect were studies on unequal conditions in the agrarian sector and on unequal exchange between advanced and less developed economies. Inequality studies slowly reemerged only in the late 1980s and the 1990s, in particular in terms of income convergence between developed and less developed economies. The chapter concludes by discussing how inequality became a central question of development discourse at the turn of the twenty-first century.