This article explores coalition dynamics in the negotiations leading up to the international Anti-personnel Landmines Convention and the Rome Treaty for an International Criminal Court. It discusses how "core" coalitions in the two cases formed and how these coalitions acquired international support and legitimacy. It suggests that multilateral negotiation processes on human security issues reflect a new kind of dynamics in multilateral negotiation processes where successful international coalitions draw strength and legitimacy through numbers and the mobilization of "boundary role" players in civil society and non-governmental organizations. The article also suggests that didactic leadership has a critical role to play in assembling these coalitions and generating the requisite levels of international attention and support to carry human security initiatives forward.