More than 65,000 people from Northern Ireland applied for an Irish passport in what has been a bumper year for the Republic's passport office.
Demand for Irish passports soared to a record high in 2016 -and the peak surge came in May following the UK's vote to leave the European Union.
However, the Irish Department of Foreign Affairs said the UK's split from Europe was only one factor.
In total 740,000 passports were sought in the year to December 21.
Some 65,136 of those were from Northern Ireland and another 59,377 from people in Britain with Irish roots.
Ireland's Foreign Affairs Minister Charlie Flanagan said: "It's been a very busy and challenging year for the passport office, but I'm pleased to say that they've met all challenges presented to them.
"There was increased demand for a variety of reasons - the Euros, the Olympics, and I acknowledge that Brexit may have played a significant role.
"I do stress, however, that we don't know for certain, as we don't ask people why they want a passport, merely whether or not they're eligible for one."
Brexit was widely seen as a driver of demand in the weeks and months after the June referendum with the number of new applicants in that time up 17,300 compared to the same period in 2015.
Other statistics show significant fluctuations at different times in other years.
The passport office's figures for 2016 showed that May was the busiest month as 96,356 applications came in. There were also surges in August, October and November.
Anyone born on the island of Ireland, or whose parents are Irish, automatically qualifies for citizenship. In some cases those who have an Irish grandparent can also apply - known in some quarters as the Cascarino effect, after Millwall and Aston Villa player Tony Cascarino claimed Irish citizenship through a grandparent to turn out for the Republic of Ireland in the late 1980s and early 1990s.
One in four people in Britain is said to have Irish heritage.
Diplomatic staff in Dublin were forced to issue an appeal for calm in the days following the Brexit vote after post offices ran out of Irish passport application forms because of an initial surge.
The Department of Foreign Affairs also said the introduction of a passport-sized card this year, accepted in 31 countries, was also a big success with 25,000 people now carrying them.
But Mr Flanagan said: "One anomaly is that some 75% of the take-up for the passport card is male. So we'd like to see more women, and more people in general availing of that. Our DFA travel wise app has also been a huge success - downloaded by nearly 10,000 people."
In June DUP MP Ian Paisley advised constituents to get a Republic of Ireland passport if possible. He posted on Twitter: "My advice is if you are entitled to second passport then take one. I sign off lots of applications for constituents. My advice is to take as many as you can especially if you travel to different world trouble zones."
Mr Flanagan said he expects the growth in application to continue in 2017.