Slovenia is voting on whether to adopt a law restoring residency rights to thousands of people erased from the national register after independence.
Loss of residency meant thousands of minorities had no rights
About 18,000 members of other Yugoslav nationalities lost the rights in 1992, the year after Slovenia declared independence from Yugoslavia.
The referendum has sparked a heated political debate in Slovenia.
The ruling centre-left coalition has called on the electorate to boycott the vote, which is expected to fail.
Loss of rights
The opposition Slovenian National Party has warned that if the law is passed it could pave the way for thousands of people to claim financial compensation.
And Prime Minister Anton Rop's Liberal Democrats party says that the referendum will provide no solution for those who lost their rights.
The referendum was drafted after Slovenia's constitutional court last year ordered that the rights of the group, known as "the erased", be restored.
After Slovenia's relatively bloodless independence bid in 1991, ethnic Slovenes were automatically granted citizenship, but r people from other ethnic backgrounds - such as minority Croats, Serbs and Bosnians - were required to apply for citizenship.
Those who had not done so within a year were removed from the national register without any public announcement.
The loss of residency meant thousands no longer had access to pensions and health benefits and many lost their jobs.
Unofficial results from the polls are expected later on Sunday.