The Nice Treaty has been accepted by voters, with a Yes vote of 62.89%. Total turnout was 48.45%.
With results in from all 42 constituencies, 906,318 voted Yes, while 534,887 have No. The formal announcement of the national result is not expected until later this evening.
The constituency with the highest turnout - Dun Laoghaire - also had the highest Yes vote, at 73%; while the constituency with the lowest turnout, Donegal North East, also had the lowest support for Nice, at just 52%.
The margin of victory for Nice was emphatic throughout the country – 63% in Dublin, 64% in the rest of Leinster, 62% in Munster, and 60% in Connacht/Ulster.
In the first Referendum on the Treaty, all but two constituencies voted against Nice, and the national vote was 54% No, to 46% Yes.
The Taoiseach has said the Irish people have given an emphatic yes to EU enlargement, and welcomed what he called the "excellent turnout".
The European Movement said that the tremendous take-up of information on the treaty, provided at its public meetings and its public information office, confirmed the wishes of thousands of Irish citizens to become more engaged in and aware of Ireland's role in Europe.
It said this interest must be maintained and increased in the future.
