Government proposals to formalise rights for same-sex couples prompted the petition. Around three-quarters of a million people signed it - out of a total population of just over 4 million. The Catholic Church is a key part of Croat identity - and many people are socially conservative.
The referendum is an enormous embarrassment for Croatia's government. It tried - and failed - to block the vote through the courts.
Success is a relative concept. Croatia appeared to be moving in a different direction to other western Balkan countries when it joined the EU in July. Now, like its neighbours, Serbia and Montenegro, it has a constitutional ban on same-sex marriage.
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make official
a document signed by many people that asks someone in authority to do something
(here) very important part
(here) people who are traditional and who do not like change
feeling of being ashamed by what it (the government) has done or what has happened to it
to stop
an idea that can mean different things to different people
a law which people of a country must follow that officially says they cannot do something