The La Grande Odyssee (The Great Odyssey) is an 11-day trek over a 670 kilometre (415 mile) course which organisers say feels more like 1,000 km for the dogs and their handlers because of its 20,000 metre elevation.
Racers, known as mushers, have come from Switzerland, Czech Republic and Spain as well as France for this year's event, which began on Saturday with fireworks before dawn in front of a large crowd at ski resort Les Carroz.
"It's really hard to hold on to them on the start line, meaning the training was a success," 41-year-old musher Remy Coste said of his pack of dogs.
The Frenchman was the early leader of the event, which was first held in 2005 and features many stages raced in darkness.
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Dogs wore flashing lights on their collars and mushers used head torches to help navigate the tricky, snowy terrain.
"Going downhill you have to be careful because it's very slippery," said French handler Jean Combazard.
"The dogs can hurt their shoulders if they go too quickly."
This year's run ends on Jan. 18 at Bonneval sur Arc.
(Writing by Patrick Johnston in LONDON; Editing by Ruth Pitchford)
