[영문]This article deals with the institutional change of 27 political systems in postcommunist countries, 1990?2002. The authors show that institutional change after the institutionalization of the postcommunist regime is limited and lock-in effects are strong. This applies to the more democratic and affluent countries as well as to the more authoritarian regimes. The authors do not find evidence for theories of institutional change that see institutional development as a linear function of socio-economic factors such as affluence or of domestic political power distribution. The European Union and NATO have an effect that is limited to the overall democratic character of the system.