Sylvester Stallone was an extra in this movie. He shares a scene with Camilla Sparv and Robert Redford. Seven years later, the producers of Rocky (1976) wanted Redford cast in the role of the film's title character Rocky Balboa but Stallone was determined he wanted to star in it. He did, and he became a big Hollywood star.
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.
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.
Debut theatrical feature film of Sylvester Stallone who appears uncredited as an extra in the movie playing a restaurant patron. Stallone can be seen wearing a suit eating dinner in a restaurant seated at a table near Camilla Sparv and Robert Redford.
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.
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).
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."