[Marc]

Harold Mendenhall, 84, started giving blood on July 7, 1977, according to the Palm Beach Post.

Last month, he reached 100 US gallons (83 imperial gallons or 666 pints).

Mr Mendenhall started giving blood when his wife Frankie was diagnosed with breast cancer.

When she died seven years later, Mr Mendenhall says he was lost.

He stopped by the blood bank on his way home from work and was soon donating up to 40 pints a year.

He said giving blood helped him cope with the loss of his wife and, later, his two sons.

"For some reason, I'm still here and I'm grateful," he said. "That's one of the reasons I keep donating."

Mr Mendenhall is especially coveted because he donates blood platelets - small cells in the blood which help with clotting.

As well as saving the lives of others, there are financial benefits for donors in Florida.

The local blood bank runs a reward programme, offering coupons for meals at restaurants.