Switzerland is to hold an historic vote on giving monkeys "fundamental rights".
Citizens will decide on amending their region's constitution to include "fundamental rights to life for nonhuman primates ".
The vote in the northern half-canton of Basel City was given the go-ahead by the country's supreme court.
It was triggered after animal rights group Sentience Politics campaigners gathered 100,000 signatures backing the move.
The animals are "highly complex beings, possessing an intrinsic, essential interest in living a life of bodily and mental integrity", said the group.
Cantonal - or state - and city governments opposed the vote saying it could violate federal law.(Image: Getty Images)
A Basel court last year dismissed a complaint against the legality of the initiative
And Switzerland's top court has now rejected an appeal against that ruling.
The court said in a statement: "In principle, cantons can go further than the protections guaranteed by the federal constitution.
"The initiative does not ask that federal rights accorded to humans be extended to animals, but is asking for the introduction of specific rights for non-human primates.(Image: Getty Images)
"While unusual, this does not in itself contradict the superior law."
Sentience Politics told the ATS news agency it was "thrilled at this historic decision".
It remains unclear when voters will have their say.
Switzerland stages popular votes and referendums at the national, regional and local levels every few months.
The process can take years from when causes get the necessary number of signatures backing them.