How effective and relevant is European Union political conditionality for the promotion of democracy in third countries? This article reports the results of a panel study of 36 countries of the East European and Mediterranean neighbourhood of the EU for the years 1988—2004. The analysis shows robust and strong effects of EU political conditionality on democracy in the neighbouring countries if the EU offers a membership perspective in return for political reform. Absent the offer of membership, however, EU incentives such as partnership and cooperation do not reliably promote democratic change. The analysis controls for economic development and transnational exchanges as two alternative potential causes of democratization. Although economic and geographical factors have an impact on democratization in the European neighbourhood as well, EU political conditionality remains a significant influence.