Thesis: This dissertation examines the economic impacts of Civil Union (pacs) and marriage in France. It is divided into three chapters. Chapter 2 evaluates the effect of taxation on the number of pacs contracted in France. Chapter 3 aims at determining if the pacs is a substitute to marriage. On that purpose, it analyzes the evolution of marriage rates and the evolution of the age at first marriage since the pacs has been created in 1999. Chapter 4 questions the economic impact of marriage : it estimates the impact of marriage on credit constraints of couples. Taxation had a clear impact on the increase in the number of contracted pacs by year. But the evolution of the number of pacs has not decreased the number of marriages. The recent trends exhibit declining marriage rates and increasing ages at first marriage but they are a continuation of previous trends observed for the last 25 years. The decline in the marriage rates, joined with the development of cohabitation introduces a difference between unmarried and married couples. The latter are more likely to form investment projects but they do not benefit from their marital status on the credit market. They suffer bad terms of credit, indicating that marriage selects couples more willing to invest in housing.