Marriage choice plays a crucial role in the formation and decay of social classes. Endogamy, the custom forbidding marriage outside one’s social class, is thus central to social history. The study considers the factors determining who married whom, whether partner selection has changed over time and regional differences between Europe and South America. The volume also questions to what extent these factors have changed over the past three hundred years. The case studies presented are preceded by a state-of-the-art theoretical introduction on the determinants influencing trends in social endogamy. Each contributor has employed the same social-class scheme and thus the volume is the first comparative study of social endogamy in an historical context.