Smokers looking to kick the habit have been invited to join a major new study in Sheffield.
Sheffield Hallam University has started a trial to see how effective e-cigarettes are at helping smokers quit, and what effect they have on the body.
Some 70 people have already signed up but around 200 more are being sought to get involved in the two-year study, funded by Heart Research UK.
Participants will get free help to quit from an experienced advisor, using either e-cigarettes or the NHS stop-smoking services.
As well as examining at how e-cigarettes are as a device to quit smoking, the trial will explore the effects on the arteries and small veins of those using the electronic devices.
Dr Gareth Jones, who is leading the study, said e-cigarettes were used by more than 2.8 million Britons and had become the most popular method for those looking to quit smoking.
But he said little research had so far been carried out into their effect on the body, and this would be the first major study to investigate the potential risks.
Those taking part will be randomly allocated to one of three study groups.
One group will receive free nicotine-rich e-cigarettes and refills for three months, along with advice on how to successfully stop smoking.
Another group will get similar advice plus complimentary nicotine-free e-cigarettes and refills for three months.
The third group will be referred to the existing NHS stop smoking service, the cost of which will be reimbursed.
Assessments will take place at Collegiate Hall in the Collegiate Crescent campus of Sheffield Hallam University.
To see if you are eligible, and to sign up, visit https://ecig2017.wordpress.com/about/ or contact Dr Gareth Jones by calling 0114 225 4312 or emailing HeartResearch@shu.ac.uk.