It is a referendum that's been called unlawful and illegitimate.
A vast majority of Bosnian Serbs have voted to preserve January 9 as a national holiday.
That is when in 1992 Bosnian Serbs declared the creation of their own state, igniting a three-year war that killed 100,000 people. Bosnia's top court had ruled against the vote, saying the holiday discriminates against non-Serbs.
But the Serb Republic president still went ahead.
Some see it as a challenge to the Dayton peace accord, which ended the war in 1995.
Bosnian Serb leader Milorad Dodik has been accused of threatening that agreement, and using the referendum to increase his party's support ahead of local elections.
So, what is behind this vote and what does it mean for the Dayton peace deal?
Bodo Weber - Democratization Policy Council
Emir Suljagic - Former Minister of Defence and survivor of the Srebrenica massacre
Tim Judah - Author of The Serbs: History, Myth and the Destruction of Yugoslavia
Source: Al Jazeera News