Constituent conventions have traditionally occupied a privileged position within normative theories of constitution-making. It is claimed that compared to a constituent legislature, an assembly specially commissioned to write a constitution is better able to reflect citizens' preferences and promote an impartial constitutional design. This article argues that the superiority of conventions over any type of constituent legislature has no support on either theoretical or empirical grounds. It also proposes that conventions may incur significant risks when a constitution is replaced within a democratic regime. Conventions often transgress their mandate by asserting their right to express or submit their decisions to the legally unbound power of the people. This claim to incarnate or represent the sovereign popular will increases the likelihood of conflicts between the convention and established institutions and, most crucially for the preservation of democracy, facilitates the use of this body by a dominant political group to legitimize its capture of state power. These arguments are supported with a critical analysis of the alleged virtues of conventions, a discussion of the history and theory of these bodies in the USA, and a comparative study of recent cases of constitutional replacement by conventions in Latin America.