People in the Irish Republic are voting in a referendum on whether to ratify the European Union reform treaty, in a poll anxiously watched across the EU.
All of the main Irish parties back the treaty but the No campaign has been putting up a strong challenge.
With many voters undecided, opinion polls suggest the result will be close.
The document, known as the Lisbon Treaty, replaces a more ambitious draft constitution that was rejected by French and Dutch voters in 2005.
It provides for a streamlining of the European Commission, the removal of the national veto in more policy areas, a new president of the European Council and a strengthened foreign affairs post.