Ireland is going to the polls in the crucial Lisbon Treaty referendum re-run which will have far-reaching implications for the future of the European Union.
For the second time in almost 18 months, around three million Irish citizens will be asked to determine the fate of around 500 million people across the EU.
Pro- and anti-treaty activists will be making frenetic final appeals to voters across the state in a last-ditch effort to woo the undecided.
Polling stations in 43 constituencies across the country will not close until 10pm to allow workers plenty of opportunity to cast their votes.
Taoiseach Brian Cowen has pleaded with the electorate to get out and back the charter, claiming the issue is too important to sit on the sidelines.
"The outcome will determine the future direction of our country and I am urging people to go out and vote and to think clearly before making this vital decision," he said.
"I am appealing to every person in this country who believes that Ireland and Europe are better together to help achieve a Yes vote."
The future direction of the European project depends on the outcome of the Lisbon Treaty vote, with a second rejection expected to plunge the union into an institutional crisis.
The Irish Government claims there is no back-up plan if the Irish vote No again, with Mr Cowen ruling out a third referendum.
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Pro-treaty groups say the charter will streamline EU decision-making, with voters' concerns assuaged by the legal guarantees - commitments from EU leaders that each member state would retain a commissioner and the charter would not effect Irish neutrality, tax rates or family law. But the No camp claims nothing in the treaty has changed and it remains a bad deal for Europe and Ireland.
