At The Saltmarket, 15-year-old twin sisters Eilidh and Louise Steel will sound an air horn to start Race for Life 5K, 10k and Family 5K events.
Eilidh flew to Florida for 11 weeks of proton beam therapy after a cancerous tumour was discovered in her neck.
And her sister Louise stood by her every step of the way.
The twins will start the races for the day at 9.30 am at Glasgow Green.