Change in marriage and cohabitation began in France thirty years ago. 2.5 million cohabiting couples and more than 40 per cent of births outside marriage reveals not only a new acceptability of cohabitation and family formation out of wedlock, but a new social signification of marriage itself. In this paper, we analyse what appears to have been a 'soft' revolution, widely accepted, and a paradoxical mutation. While the abandonment of a strictly matrimonial conception of the family is generally accepted in France, attitudes are much more contradictory with respect to legal rights of unmarried couples. The long, complex and controversial story of the evolution of the Pacs (Parte Civil de Solidarité, shows, behind the issue of homosexuality, how difficult it is for French culture to conceive a legal status of non-married couples. The Pacs, as a new possibility for heterosexual as well as homosexual cohabitees, is not easy to define from a legal point of view. This intermediate status, neither a union nor a contract, neither private nor public, expresses the ambiguity of the French way of responding to increasing cohabitation. Analysing the Pacs as a transitory law, we suggest that a complex jurisprudential story is now beginning in France. This paper ends with a broader perspective on the interpretation of family change: no consensus exists in academic and political circles. The new forms of social inequalities will certainly represent one of the main issues in the public, academic and political debate in the future.