During the filming of the scene where Maria attempts to escape through a canyon wired with dynamite, Claudia Cardinale's stunt double was badly injured during the explosion. Cardinale, who had never ridden a horse before, performed the stunt herself for the final cut, and escaped uninjured.
First western to feature nudity although it is a long-range view and tame by later standards.
The success of the movie led to calls from the studio for a sequel, but only with the four principals actors involved because of the fiasco surrounding the sequel to Die glorreichen Sieben (1960), where only Yul Brynner returned. However, all of the principals had full filming schedules. By the time any space could be cleared, Robert Ryan's health (due to lung cancer) made it impossible for him to perform the physical work necessary for the movie. After his death in 1973, all plans for a sequel were scrapped.
Lee Marvin took it upon himself to keep the film's guns clean in the unpredictable desert conditions.
Despite the principal male actors being in their 50's (except for Lee Marvin, who was only 42), all of them insisted on performing their own stunts. However, only Woody Strode performed all of his stunts as there were no black stuntmen who came close to his height and stature. Burt Lancaster, who was 52 at the time, did most of his own stunts, including being hung upside down in Coyote Pass and running across the top of the moving train car. The studio balked, however, at Lancaster climbing the side of the cliff in the pass to plant the dynamite and a stuntman was substituted. Even though Jack Palance was as tall as Strode, he had to use a stunt double for the scenes where he was wounded and fell off his horse, because falling the wrong way off a horse could lead to serious injuries.