What are the “roles” and “responsibilities” of the nuclearweapon possessor States (NWPS) and the non-nuclear-weapon States (NNWS)? While there may be several different ways to address these questions, for purposes of this presentation, it might be useful to categorize the roles of the NWPS into two separate but related aspects: the roles of the five nuclear-weapon States (NWS) as defined under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), under nuclear-weapon-free zones (NWFZs), in their capacity as the permanent members of the United Nations Security Council, plus as providers of “extended deterrence”; and the roles of the remaining four NWPS in contributing to regional and global security. The roles of the NNWS are quite clear under the NPT and NWFZ treaties, but there arise questions about the roles of some 33 NNWS that are parties to nuclear-armed alliances/arrangements and as such rely on extended nuclear deterrence or security provided by their NWS patrons. In addition, one may also consider the roles of both NWS and NNWS under the NPT and NWFZs. Finally, one might also consider the roles of all NWPS and NNWS.