Voters in Switzerland have strongly backed a new law permitting research on the stem cells of human embryos.
Some say the backers of stem cell research are offering false hope
Two-thirds of voters said "yes" to the government's proposals, opposed by religious and left-wing groups.
Nationwide referendums are common in Switzerland, but this vote makes it the first country in the world to put the controversial issue to a popular vote.
Scientists believe stem cells may hold the key to treatments for illnesses including Parkinson's and diabetes.
Switzerland, which is a world leader in medical and pharmaceutical research, has so far not permitted research on human embryos.
For and against
Opinion polls had indicated the Swiss were deeply divided and more than 20% said they were finding it hard to decide how to vote on an issue which many regard as ethical as well as scientific.
In the end, the result - a 66.4% approval - was a surprise, says the BBC's Imogen Foulkes in Berne.
The Swiss government, the universities and the pharmaceutical industry all urged support for embryonic stem cell research.
They said Switzerland, with its long tradition of medical research, should not be left out of such potentially ground-breaking work.
But the Catholic Church, Switzerland's influential Green Party and medical ethics groups oppose the new law.
Many say the claim that stem cell research could bring cures for illnesses is offering false hope to sufferers, and they suggest cloning will be Switzerland's next step, our correspondent says.
The proposals are strict. Research would be permitted only on cells from embryos less than seven days old which were left over from fertilisation treatment and due for destruction anyway.
Countries such as Britain and Sweden already have much more relaxed laws.
For many people, research into human embryos is about more than science and economics, our correspondent says.
It raises profound questions about the best way to value human life, she says.