The eastern enlargement of the European Union is a twofold process, in which governments of transition countries decide whether or not to apply for membership and in turn EU members decide whether or not to accept these applicants. The authors argue that the level of democracy and the extent of market reforms together determine the first decision, while the second decision is largely determined by the EU observing the reform process in applicant countries imposed by the acquis communautaire conditionality. The natural procedure to test this theory is a Heckman selection model. A Heckman specification with panel probit estimators in both stages is used. The data supports the argument that uncontested reforms signal the policy support of relevant political parties to the EUand increase the likelihood of joining the Union. The authors also test for specification errors and check the robustness of the findings.