This chapter deals with the implementation process of affirmative action measures in Argentina, Chile, Colombia and Peru. Despite their liberal jurisprudence tradition, constitutional interpreters (e.g. judges, lawyers, scholars) and policy-makers have made room for affirmative actions by constructing the right to equality before the law in terms other than formal equality. The chapter examines the origins and evolution of affirmative action in the countries under analysis. It reviews their constitutions and judicial decisions to determine the legal foundations of these policies, their challenges before national courts and the role of judges in determining their legal foundations. The analysis then turns into issues of design, implementation and efficacy by focusing on specific recipients of affirmative action policies in the countries and whether their constitution identifies them as vulnerable groups. Finally, the chapter explores the impact of cultural and budgetary implications of affirmative actions as determinants of the implementation process in the chosen countries.