This chapter discusses the relative neglect of empirical research on same-sex couples in debates about their rightful legal treatment. It raises the difficulties that undertaking such engagement might engender. The chapter calls for disaggregating the legal content of marriage for the purposes of analysis. By reference to the findings of social scientists, the chapter sets out the evidentiary basis for challenging the assumption that access to marriage on the existing terms best remedies same-sex couples’ long-time legal neglect. The chapter flags crucial methodological difficulties with the enterprise of looking to research in order to assess the fitness of existing marriage law for same-sex couples. It highlights important considerations relevant not only to the question of same-sex couples, but also to that of cohabitation and to other boundary troubles raised by law’s regulation of intimate life.