In 1999 three East-Central European states (Poland, Hungary, and the Czech Republic) gained membership in the North Atlantic Treaty Organization. Since then, they have been consumers of rather than contributors to security. In its 2002 Prague Summit, NATO is expected to invite several additional post-communist states. Professor Barany argues that, once it began, the Alliance should continue the enlargement process. Nevertheless, he maintains that only states that satisfy NATO’s membership criteria should be allowed to join. Through an extensive analysis of four NATO aspirants (Bulgaria, Romania, Slovakia, and Slovenia), Barany demonstrates that they are in several important respects unprepared for membership and that there is no pressing reason for NATO’s haste and, while making clear that its doors remain open to qualified candidates, the Alliance should hold off further expansion until prospective members will become assets rather than liabilities.