Before filming began, director Alejandro Jodorowsky spent a week without sleep under a Zen Master's direction and lived communally with the film's cast for a month.

At a projected budget of $1,500,000 (in USA dollars), it was to have been the most expensive Mexican film production to date. The film reportedly cost only half that amount.

The crucified animal carcasses were borrowed from a local restaurant, which were then served to customers upon being returned.

During the boating sequence, Jodorowsky had intended to shoot a scene where the group leaps into the ocean to "get in the infinite waters." The cast proceeded to leap in, then promptly began to drown. The crew was so busy trying to rescue them that nothing of the scene ended up being shot.

The movements from the opening scene ritual are actual movements of a Japanese tea ceremony. Jodorowsky states that the girls themselves were not actual actresses, merely two people who "wanted to have a spiritual experience. They were searching for their own truth, the naked truth."

Jodorowsky recalls that the lizard and toad circus was difficult to prepare for and film. The toads themselves were hard to dress, as "their urine was like acid," and they'd keep filling up with air and then blowing it out, trying to escape. The lizards, on the other hand, were incredibly sedate, and the cameraman would have to leave the camera rolling for long periods of time before they'd even flick their tongues or move their eyes.

The film is based on "The Ascent of Mt. Carmel" by St. John of the Cross and "Mt. Analogue" by Rene Daumal.

During Axon's hallucination, the battling dogs were indeed real fighting dogs.

The chanting audible during the opening ritual scene includes the lineage of Buddhist teachers. Jodorowsky's name appears exactly as the chant says "Shakyamuni," which refers to Siddhartha Guatama, the historical buddha who reached nirvana while meditating beneath a bodhi tree.

"Axon" is the name of the structures that transmit impulses between nerve cells.

Brontis Jodorowsky should have been in the movie but, as he says, his scene was cut because a girl of his age appeared naked in bed. Only her butt could be seen, but her mother tried to get money saying that her daughter was traumatized. But he knew her because she was in his school, and she was not traumatized. Well, in the end she didn't win the trial and they didn't give her money, but the judge said they had to cut the scene and so Brontis didn't show up.

Debut of Arielle Dombasle.

George Harrison, himself a big fan of Jodorowksy's work after having seen El Topo (1970), was originally up for the role of The Thief, but disagreed with the director over what he considered gratuitous nudity - particularly, the shot where his anus is bathed. Rather than cast a stand-in, or remove the shot altogether, Jodorowsky stood his ground, prompting Harrison to drop out. Jodorowsky later expressed some regret over this in the Anchor Bay DVD commentary, noting that Harrison's involvement could have exposed the film to an even larger audience.

During the decapitation scene, the actor actually struck Jodorowsky for real, cutting his neck and nearly killing him. Jodorowsky reflects that had the sword actually been real, he would indeed have been decapitated.

The crew didn't obtain any permits for the shot of the helicopter setting down in the street, merely had an actor in a police uniform stop traffic while they filmed, then proceeded to run off after the shot was complete.

The "tumor" that the priests pull out of the back of the Thief's neck was an octopus the filmmakers purchased at a local market.