In this article I examine the view, common amongst several contemporary legal positivists, that rules of recognition are to be understood as conventional rules of some kind. The article opens with a discussion of H.L.A. Hart's original account of the rule of recognition in the 1st edn of The Concept of Law and argues that Hart did not view the rule of recognition as a conventional rule in that account. I then discuss Hart's apparent turn towards a conventionalist understanding of (...) the rule of recognition in the ‘Postscript’ to the 2nd edn of The Concept of Law, and attempt to cast doubt on the strength of Hart's commitment to such a turn, and on the reasons prompting him to make it. Finally, I consider one of the most interesting contemporary conventionalist accounts of rules of recognition, namely Andrei Marmor's view that such rules should be understood as the constitutive conventions of partly autonomous social practices. My aim in this part of the article is to compare Marmor's account with my earlier interpretation of Hart's views, and to consider whether Marmor's account truly is conventionalist in character and whether it provides us with a persuasive conventionalist understanding of rules of recognition. (shrink)