The paper focuses on the effects of NATO's decision to enlarge on several states and populations invited to join or that had wanted to join but were not invited at the Madrid summit: Poland, The Czech Republic, Hungary, Slovenia, and Romania. Within the larger framework of alliance theory and the overall transformation of NATO, the authors judge the impact of the Madrid summit decisions on the five countries in three areas: domestic politics (who wins and who loses); international behavior (the way that the foreign policy of each country is likely to be affected by the Madrid decisions); and the role that each country is likely to play as an alliance member or as a "close partner." Since the effects of the Madrid decision will vary, the alliance faces different problems in each of the five countries, ranging from overcoming considerable public doubt about the wisdom of NATO membership in the Czech Republic and Hungary to handling the potentially volatile disappointment in Romania. Further politicization of issues of cost of enlargement and the course of NATO's transformation is likely. In other words, the "politics" of NATO enlargement has just begun.