The counting of votes will begin on Saturday morning local time (Saturday night NZT), with a result expected early on Saturday evening (Sunday morning NZT).
It is quite likely that if the Eighth Amendment is repealed there will be hardly any doctors willing to carry out abortions; no doubt that would prompt another campaign to remove their "right to choose".
Several activists held a large "Welcome Home" banner, while others held a placard reading "Thank you for making the journey so other women don't have to" - a reference to the way Irish women seeking abortions have had to leave the country to obtain them.
The vote pitted conservative backers of strict abortion restrictions against those supporting a woman's right to choose. For opponents, it would be a betrayal of Ireland's commitment to protect the unborn.
The law on abortion is enshrined in the country's constitution, which can be changed only by referendum.
An Irish Times/Ipsos MRBI exit poll suggested that voters in the once deeply Catholic nation had backed change by 68 percent to 32 percent.
RTE's exit poll suggested 69.4 per cent in favour of the Yes side in the referendum and 30.6 per cent for "No".
Chris Garvin, 20, who works in human resources, said: "I'm not going to try and sway people's opinions but it's a very, very important matter and I think it's going to affect everybody's lives in some way".
If the victory is officially confirmed, Ireland's government says it is committed to introducing unrestricted access to abortion for women up to 12 weeks pregnant.More news: Judge sides with parents, boots adult son from NY home
Some figures suggest as many as nine women a day travel from Ireland to the United Kingdom to terminate a pregnancy. This is despite the fact that a baby needs more protection, not less, than an adult; repeal would give the mother, or those "advising" her, the power of life and death over the baby. The "X" case in 1992 involved a teenager who had been raped, who made a decision to travel to the U.K.to obtain an abortion - and found herself being stopped by the Attorney General from leaving the country. The Eighth Amendment - the constitutional provision protecting the right to life for the unborn - was passed that same year with 67 percent approval.
"I don't think a human life should be simply. down to being unwanted or not [,] and yes it's much so hard for women in those positions".
If the amendment is removed and the issue moves to parliament, the government proposes that terminations be allowed during the first 12 weeks of pregnancy.
Thousands of Irish women every year cross the channel to have an abortion in the UK.
They're flying home because Ireland requires people to be in the country to vote in referendums, unlike other countries that allow overseas voting. "Please please vote Yes this Friday".
Many contend that criminalising abortion does not stop it.
John McGuirk, communications director for the "Save the 8th" campaign pushing a "No" vote, reacted to the exit poll on Twitter.