The course was 5,000 metres above sea level, and at that height the temperature is below freezing and there is half as much oxygen as normal.
If a normal climber was to walk the course it would take them two or three days, but organisers were hoping the winner of the race would finish inside four hours.
50 years since first climb
The race is happening to remember the first successful climb of Mount Everest, which happened on 29 May 50 years ago.
New Zealander Sir Edmund Hilary was the first man to reach the top of the mountain, accompanied by a local Nepalese man called Tenzing Norgay.