This work compares union dynamics in western Germany and France. The aim is to study the pattern of first union formation in both countries by describing and evaluating the most important factors and settings that determine possible differences between both countries. Even though marriage, cohabitation and childbearing have undergone massive changes in western Germany and France, striking differences remain. The impact of various explanatory variables - such as education, employment or the occurrence of a pregnancy - on union formation is strongly dependent upon the specific context.