Turnout during the Irish vote was being watched intently across Europe
People in the Republic of Ireland have voted in a referendum on whether to ratify the EU reform treaty.
The BBC's Jonny Dymond in Dublin says all eyes are on the turnout, as a low figure would suggest a rejection which could plunge the EU into crisis.
Some reports suggest Thursday's voter turnout was about 40%. Results are expected later on Friday.
All 27 member states have to ratify the treaty for it to take effect, but only Ireland has held a public vote on it.
The treaty is aimed at streamlining decision-making in the EU to cope with its expansion into Eastern Europe and would reduce countries' veto powers.
The Lisbon Treaty replaces a more ambitious draft constitution that was rejected by French and Dutch voters in 2005.
Opinion polls suggesting the referendum's result is too close to call, despite a high-profile "Yes" campaign led by Prime Minister Brian Cowen which had the support of most of the country's main parties.
Mark Mardell on what would sway the vote
Any turnout higher than 40% will bring a smile to the Yes campaign, our correspondent says.
The treaty 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. Fourteen countries have completed ratification so far.
Irish polls closed at 2200 (2100 GMT) and counting starts on Friday morning, with the result expected soon after 1530 (1430 GMT).
RTE reported turnout was "brisk" in Kilkenny and Wicklow, but in many other areas, including Cork, Meath and Louth, it was slow.
Voting No because you don't know... is an idea that seems a long way from the dispassionate debates in Brussels
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