The article describes the rise of unmarried cohabitation in Latin American countries during the last 30 years of the twentieth century, both at the national and regional levels. It documents that this major increase occurred in regions with and without traditional forms of cohabitation alike. In addition, the striking degree of catching up of cohabitation among the better-educated population segments is illustrated. The connections between these trends and economic (periods of high inflation) and cultural (reduction of stigmas in ethical domains) factors are discussed. The conclusion is that the periods of inflation and hyperinflation may have been general catalysts, but no clear indications of correlation were found between such economic factors and the rise in cohabitation. The shift toward more tolerance for hitherto stigmatized forms of conduct (e.g., homosexuality, euthanasia, abortion, singleparent household) is in line with the rise of cohabitation in regions of Argentina, Chile, and Brazil where cohabitation used to be uncommon. Further rises in cohabitation during the first decade of the twenty-first century are expected in a number of countries (e.g., mexico) despite conditions of much lower inflation. © 2012 The Population Council, Inc.