It is clear that unmarried cohabitation is increasing in Chile. It is less clear what unmarried cohabitation is and why is it rising. In Latin America cohabitation is common among low income groups, and has been described as a surrogate marriage for the disadvantaged. Cohabitation in the region entails conventional gender roles and having children. It has been explained by colonial dominance, poverty, kinship, and machismo. The evidence amassed here indicates that although in practice cohabitation is similar to marriage, they are not the same. In fact, cohabitation has decreased social visibility. Cohabitation does not entail any social ceremony or rite. As it is not institutionalised it remains concealed from both social recognition and social scrutiny. Thus it tolerates partners who are dissimilar, or can be sustained despite a higher level of difficulties in a relationship. The findings validate previous research as cohabitation is sparked by pregnancy, parental tolerance-mainly through not enforcing marriage-, a close mother-son bond–which inhibits marriage-, and the material costs of marriage. The research follows a life course perspective. It is based on twenty four qualitative life histories of urban deprived young people, women and men, involved in a consensual union and with children.