Natalie Wood's then husband, Richard Gregson, was one head producer on this picture. She was also a good friend and former high school classmate of co-star Robert Redford. She provided hair styles for some of the actors, provided wardrobe styles for some of the stars, and was a visible presence on the European locations for the film.
Robert Redford's character Dave Chappellet was supposedly based on two real life skiers; Billy Kidd and Spider Sabich. Kidd was the first American male to win an Olympic alpine skiing medal when he won a silver in the slalom at the 1964 Olympics. Sadly, Sabich was killed under mysterious circumstances by his lover, actress/singer Claudine Longet.
Star Robert Redford, in the audio-commentary on the DVD, reports that this film was in pre-production for a long time. He was supposed to appear in Rosemary's Baby (1968), and then this pet project of his was to go before the camera. Due to a breakdown in negotiations and his eventual refusal to appear in Rosemary's Baby (1968), this film was canceled at least twice before Redford's production company picked up the film and began moving forward with the project.
Costume Designer Edith Head had begun work on this film back in the spring of 1967 when her contract with Paramount Studios came to an end. It is debatable how much of her contribution still remains in the completed film but she regarded this film as one of her 100+ films of her incredibly long costume career.
According to the American Film Institute, "racing footage in the film is a mixture of real races (held at Kitzbuhel, Austria, during February and March, 1969) and scenes staged by the company on location in Kitzbuhel and Wengen, Switzerland. American locations were filmed in Idaho Springs, Colorado, and around Golden, Colorado."
Actress Sherry Jackson was one of the early choices to play Robert Redford's love interest but her agent rejected the deal without her knowledge. Sherry's part would have been the smaller part, as Redford's girlfriend in Idaho Springs, Colorado since the main ingenue works for the European ski maker.
The movie's name was changed to "Downhill Racer" from its source Oakley Hall 1963 novel title of "The Downhill Racers" though the two titles still remained quite similar to each other. This ends up working since the title character is really in it for himself, and sets himself apart from the other skiers (with bad attitude and apt skills) from the very beginning.
On the Denver Colorado based Country Music Radio Station that Robert Redford's listening to before meeting the local girl, a song comes on titled "It Was a Long Happy Day" by a singer named Hank Hopkins. Neither the song or the artist can be found online, so it might have been written for the movie.
There was a rumor that Sylvester Stallone can be seen as an extra during a restaurant date scene, but it's not him and hardly even resembles him. Also, it would be unlikely that an American no-name actor would travel to Europe for an extra role: that scene and much of this film was shot throughout European cities.
In real life Robert Redford has lived in a private snow-set ranch in the state of Utah, which is where another snow-set Redford movie, Jeremiah Johnson (1972), was actually filmed, it being made and released about three years after Downhill Racer (1969).