Whereas negotiated regulation of social interactions has become the issue in society as a whole, the true extension of this contractualisation of relations remains debatable. Does not the permanence of strong social determinations throw up a major obstacle? This article focuses on the contractualisation of the workings of conjugal and familial relations. It shows that the relations between spouses (and ex-spouses) are marked by a strong expectation relating to negotiation of how the couple functions, but that this cannot be turned into an exclusive model for the couple and the family. Similarly, social regulators, while constantly expressing their preference for the contractualisation of couple/family relations, remain confronted by situations in which other, less democratic, forms of regulation of the couple predominate and where it appears futile to seek to force spouses to come to an understanding.