People who are at risk of having a stroke may benefit from pre-emptive surgery, say doctors.
There has been concern that the surgery was too risky
A major trial involving 3,000 patients from 30 countries has found that an operation to stop the arteries from narrowing can halve the risk of stroke.
Some doctors have been reluctant to carry out the procedure because of the risks involved.
But this study, published in The Lancet, suggests it may have long-term benefits for some patients.
Strokes occur when the blood supply to the brain is disrupted. In most cases, this happens when a blood clot blocks an artery carrying blood to the brain.
When the blood supply is disrupted, the brain cells are deprived of oxygen and other nutrients, causing some cells to become damaged and others to die.
Some strokes are fatal while others cause permanent or temporary disabilities.
Patients with substantial narrowing of one of the main arteries, the carotid artery, are known to be at increased risk of stroke.
Half of those involved in this trial were given surgery to widen their carotid artery. The others did not.
The trial, which was funded by the UK's Medical Research Council and the Stroke Association, found that people who had the operation had a 3% risk of dying as a result of the surgery.
Over the course of five years, they had a further 3% chance of dying from stroke bringing their total risk to 6%.
However, people who did not have the operation had a 12% chance of dying from stroke over the five years.
Alison Halliday, a consultant vascular surgeon at St George's Medical School in London who led the trial, said the findings showed patients can benefit from surgery.
"It's clear from our trial that immediate surgery is the best option for some patients with severe narrowing of the carotid artery."
However, she said further research may be needed to convince doctors that it is worthwhile.
"How much this changes practice across the health service will depend on how long the benefits last.
"We're now going to follow these patients for another five years to find out."
The Stroke Association welcomed the findings.
"Each year over 130,000 people in England and Wales have a stroke, and it has a greater disability impact than any other medical condition," said Dr Joanne Knight, its associate director of research and development.
"This research shows that real results can be achieved by prioritising those patients at risk of stroke to have carotid endarterectomies.
"Whilst it's vital that patients who are eligible for such treatment are carefully selected, it adds to the growing body of evidence that preventive treatment against stroke should receive a higher priority."
A study published in The Lancet in March suggested the procedure should be carried out within weeks of any stroke "warning" signs.
Researchers from Oxford University said many patients in the UK are forced to wait months for surgery.
However, they said the NHS would need extra staff and capacity to be able to carry out the operation when patients need it.