The first Race for Life event took place in 1994, when 680 participants raised a total of £36,000 for Cancer Research UK.
There are now more than 230 races around the country which, over the years, have helped to raise more than £493 million.
Last year, Cancer Research UK spent more than £1 million in Leicester on some of the country's leading scientific and clinical research.
For example, scientists at the University of Leicester are looking for new molecules in every-day foods which could help prevent cancer.
The entry fee goes towards the cost of running the events and the charity is reliant on the sponsorship of participants to raise cash.
Katie Martin, Race for Life event manager for Leicester, said: "After the Race, we'll be asking everyone to take one last step – by returning the money they have raised so it can go into vital research to help more men, women and children survive cancer.
"Many people don't realise that their entry fee only covers the cost of staging the event. It is the sponsorship money that really makes a difference.
"Cancer Research UK doesn't receive any Government funding for its ground-breaking work.
"The money people raise through Race for Life is crucial because it means we can go on supporting the pioneering work of doctors, nurses and scientists who are fighting cancer on all fronts.''
You can pay in your sponsorship money by:
Ringing 0845 600 6050.
Sending a cheque, payable to Cancer Research UK, to: Race for Life, PO Box 442, Northampton, NN3 6UU.