It takes place once a year on either the last weekend in August or the first weekend of September in the Alps. It follows the route of the Tour du Mont Blanc through France, Italy and Switzerland. It has a distance of approximately , and a total elevation gain of around . It is widely regarded as one of the most difficult foot races in the world, and one of the largest with more than 2,500 starters. It is one race during a week-long festival based around Chamonix in France, and is a race of the Ultra-Trail World Tour. The races have strict entry and qualification requirements attained by accumulating enough race points through qualifying trail races over the previous two-year period. In 2016 and 2017, 42% and 34% of runners did not finish the UTMB race.