The literature on intergovernmental organizations (IGOs) contains three sets of mapping exercises (Wallace and Singer, 1970;Jacobson et al., 1986;Shanks et al., 1996;Cupitt et al., 1996) that delineate the constellation of IGOs operating in international affairs. While all of these efforts trace the growth of IGOs, none of them are recent enough to assess the nature of changes to these organizations since the end of the Cold War. Our purpose here is two-fold. First, we create a new mapping process that allows us to identify the range of changes that may have occurred in the constellation of formal intergovernmental organizations over the first 15 years of the postCold War era and compare the patterns we uncover to those of the 15 years immediately preceding the Cold War's end. Second, we compare changes and continuity in state membership in these organizations. Chapter 3 will then both propose an explanation for the patterns we uncover and probe some consequences of these patterns for post-Cold War international politics.In addition to a more recent empirical time frame, we differ from previous efforts in four ways. First, we conceptualize the universe of relevant