What impact has the 2004 enlargement had on legislative decision making in the European Union (EU)? This study answers this question by examining the controversies raised by a broad selection of legislative proposals from before and after the 2004 enlargement. The analyses focus on the alignments of decision-making actors found on those controversies. Member State representatives, the European Commission and the European Parliament vary considerably in the positions they take on controversial issues before and after enlargement. Consistent patterns in actor alignments are found for only a minority of controversial issues. To the extent that consistent patterns are found, the most common involve differences in the positions of Northern and Southern Member States and old and new Member States. The North-South alignment was more common in the EU-15 and reflected Northern Member States' preference for low levels of regulatory intervention. The new-old alignment that has been evident in the post-2004 EU reflects new Member States' preference for higher levels of financial subsidies. This study argues that the persistent diversity in actor alignments contributes to the EU's capacity to cope with enlargement.