After years of relative stability in terms of both mission and membership, NATO is undergoing rapid change in both areas, primarily because of the end of the Cold War. Currently, the most important membership issue involves the inclusion of former Cold War 'enemy' states from Central and Eastern Europe. In addition, NATO has, in effect, become a peacekeeping arm of the United Nations in Bosnia, a mission that was certainly not anticipated within the original NATO charter, as well as a peacemaker in Kosovo. These critical changes may have profound consequences for NATO's future. In this article we explore the attitudes towards NATO of a cross-national sample of international relations scholars and practitioners drawn from NATO nations. Taking the same approach used in Vincent's studies of UN delegate attitudes, we apply 'capability theory' to the observed variation in attitudes towards NATO's decisionmaking structure. That is, we expect that the critical explanation of the division of attitudes towards NATO's method of decisionmaking will relate to the 'capability' of the nation to which the respondent belongs. This is predicted since nations, under the theory, attempt to augment their capabilities through their membership in international organizations. It follows they will tend to value the organization to the extent of the augmentation. Because the decisionmaking rules of NATO, which are currently based on consensus, could prevent NATO from acting if a single 'new' member disagreed with a proposed NATO course of action, we feel that capability theory may be applicable, since this would affect the capabilities of the other members. In general, we find significant support for this 'capability' interpretation of attitudinal differences relating to possible alteration of NATO's decisionmaking rules.