Cannabis is going on sale in pharmacies in Switzerland as part of new research into regulation of the drug.
Long stigmatised for its illicit use, scientists are now looking at how legally selling cannabis affects consumption and health among users.
The so-called "Weed Care" study will allow 370 participants to legally buy hemp products from nine dispensaries in Basel.
Health officials hope the trial -- which gets underway on September 15 -- will address political questions about the possible regulation of cannabis, which is illegal in Switzerland except for medical exceptions.
"The first research question is whether consumption changes - whether more is consumed, less or the same amount," said Regine Steinauer, head of the addiction department at Basel University.
"And we are also investigating if the mental state or physical health changes when cannabis is consumed from the pharmacies."
Research participants are selected if they already use cannabis and must complete surveys throughout the 30-month study.
They can buy various hemp products at €8 to €12 per gram - a price determined by the current going rate on the black market.
But the participants must also adhere to monthly limits on how much cannabis they can buy.
Lukas Engelberger, medical director for Basel, said: "It's not about full legalisation - but regulation - where consumption is possible in a protected setting. That's what we want to test now."
The "Weed Care" project was approved by the Federal Office of Public Health (FOPH) in April.
Four different types of cannabis herb and two types of hashish will be available in the pharmacies, which study participants can buy after showing their ID cards.
Switzerland's health office estimates there are around 200,000 active consumers of cannabis in the country despite the drug being illegal.
In 2008, some 60% of Swiss voters rejected a proposal to decriminalise cannabis consumption in a referendum.