The contribution of thousands of men in a south Wales community to a ground-breaking medical study for the last 25 years is being marked.
Men on the study have taken part in tests every five years
The Caerphilly Study was launched in 1979 to help understand the causes of heart disease.
Since then, men have taken part in research which has made medical breakthroughs - like taking aspirin for preventing heart attacks.
They and their families have marked the study's success at a celebration.
Caerphilly was originally chosen as the centre for the study because the south Wales valleys were then a black spot for problems of heart disease, explained Professor Peter Elwood, from the University of Wales College of Medicine.
Prof Elwood has led the study, which started by concentrating on researching the causes of heart disease.
But as the volunteers have grown older, it has concentrated more on dementia and the effect of strokes or mini-strokes.
Two hundred papers detailing the study's research have been written and its contribution to medicine has been "immense", he said.
Twelve hundred of the original 2800 men aged between 25 and 49 who volunteered for the study have just completed the fifth element. Another component of the study is now planned for 2009.
"The Caerphilly Study has made a particular contribution in looking at blood clotting and thrombosis and their relation to heart attacks and strokes," said Professor Elwood.
"As the men have grown older we have turned to look at strokes and sadly, dementia.
"We know that Alzheimer's disease is a cause of dementia but strokes and mini strokes are even more important," he said.
While the study has been going understanding of heart disease has improved across the UK and Western Europe as a whole, and Professor Elwood said the Caerphilly study had contributed significantly to the body of knowledge.
Attempting to set up a similar study today would be "difficult", he said, both because of restraints imposed by the ethics committee and because of its size.
Volunteer John Parry says it has been a privilege to take part
Grandfather-of-five John Parry was 49 when he signed up for the study and he says it has benefited him as he has grown older.
"I do tend to look after my health. I don't smoke and I don't indulge too much in alcohol - although I do have a drink now and then.
"I have been very fortunate to take part in the study. It has been a privilege," said the 74-year-old.
On Thursday Health Minister Jane Hutt and MP Wayne David joined researchers, the Caerphilly men and their wives at the town's rugby club for a 'thank you' party.
"2,800 men started the study and many of them are still co-operating. They have contributed enormously to scientific research. This is a celebration and our way of sharing our thanks," said Professor Elwood.