Pier Paolo Pasolini’s “Salò, or the 120 Days of Sodom” contains some of the most repellent and disturbing imagery ever put on film and was instantly banned in Pasolini’s native Italy upon its release in 1975. But that’s not the only reason why production history alone has assured “Salò” a morbid notoriety: Pasolini was murdered under highly suspicious circumstances prior to the completed film’s contentious premiere.

“Salò” has also assumed the pinnacle of covetous film-buff fascination because, though it continues to turn up periodically on local repertory screens (most recently in Lincoln Center’s Pasolini retrospective in November 2007 and in a 2005 New York Film Critics Circle program), the film has eluded American home-video availability for decades.

A 1990s American laser-disc and DVD release of “Salò” ran afoul of licensing difficulties with the late director’s estate. The few copies released by the Criterion Collection at the time changed hands for exponentially increasing amounts of cash on the collectors’ market. Pirated copies have occasionally been available (often in adult bookstores) for more than a decade.

Today, Criterion has at long last rescued “Salò” from collector lust and paper-bag infamy via an authorized deluxe two-disc edition, boasting an immaculate transfer (the prior, short-lived legitimate release lost considerable picture quality in its film-to-digital journey) and a handful of accompanying short subjects that document the film’s conception, production, release, and legacy.

“Salò, or the 120 Days of Sodom” began creative life in a script collaboration between Pasolini and his longtime assistant, the director Sergio Citti. The project — an adaptation of “120 Days of Sodom,” the Marquis de Sade’s infamous catalog of sexual cruelties meted out by a fictional quartet of wealthy libertines on a group of young, primarily female prisoners — was initially intended as a directing vehicle for Citti.

Prior to “Salò,” Pasolini had made successive visionary, art-house-friendly, sexually graphic adaptations of Boccaccio’s “Decameron,” Chaucer’s “The Canterbury Tales,” and the Arabic folk-tale compendium “The Arabian Nights,” all envisioned as a trio called “Trilogy of Life.” But by the middle of the “Me Decade,” the director was increasingly appalled by what he saw as a covert war on personal freedoms waged by a manipulative consumerist aesthetic whose commoditizing of sexuality was having a toxic cultural effect on Europe. Adapting de Sade’s book became the artistic means to explore the enduring human capacity to rationalize the totalitarianism of unchecked greed.

Capitalism wasn’t Pasolini’s only fuel. In the mid-1940s, in an ill-fated attempt to wait out the waning years of World War II in relative safety, his family had relocated from Bologna to the northeastern town of Casarsa. Unfortunately, their adopted region fell under the control of the Italian Social Republic, the Third Reich’s last-ditch attempt to prop up Benito Mussolini and consolidate the Italian fascist state in Italy’s northern extremes.

Years later, haunted by the atrocities, losses, and deprivations of his family’s costly move (the director’s brother was killed by communist partisans while in Casarsa), Pasolini chose to set the evolving de Sade adaptation in the capital of the Nazi puppet state, Salò, a picturesque lakeside town located midway between Venice and Milan. Additionally, Pasolini lent de Sade’s rambling, nearly unreadable accumulation of depravity an ostensible classical structure by splitting the eventual two-hour movie into four sections inspired by the deepening circles of hell in Dante’s “Inferno.”

As Pasolini’s preoccupation with the project grew (the director eventually decided that “Salò” would be the first of a “Trilogy of Death” to complement and counter his three, comparatively upbeat, prior cinematic excursions), Citti’s interest waned. When the film went before the cameras in early 1975, first on location in northern Italy and then on the Cinnecitta back lot, Pasolini directed a script completed in collaboration with the writer and director Pupi Avati.

Documentary material included in Criterion’s new release shows the experience of committing “Salò” to film to have been both a grim and a giddy one. The four young victims (a balance of adolescent boys and girls in Pasolini’s update) of the fascist libertines were primarily portrayed by nonactors. “Because of all the teenagers, it was like high school,” the veteran actress Hélène Surgère recalls decades later. For her less-seasoned fellow troupers tasked with reacting to simulated sexual attacks and revolting humiliations, “the challenge was to keep from laughing.” Upon screening the finished film, Ms. Surgère wondered “how we’d made something so awful without realizing it.”

For the director, who kept the details of his scenario to himself until shortly before filming each sequence, and who covered many of those scenes with multiple cameras, the challenge was to continue “accumulating material” (as he described the on-set process) while editing the mountains of resulting footage during production. Behind the scenes, glimpses in several of the supplementary short subjects show Pasolini rehearsing, staging, and shooting the film’s final, unforgettable, ruthlessly catharsis-free orgy of rape, torture, mutilation, voyeurism, and murder with the beneficent focus of a highly professional film artist working to finish his project on schedule.

“On ‘action,’ you scream and cry and look as much as you can into the camera,” Pasolini calmly instructs a young cast member.

“Wait till you see what you do in the next scene,” the director says in a subsequent effort to deflect actor Aldo Valletti’s playful request for more screen time. “You can’t imagine.”

What no one involved could imagine was that Pasolini would not live to see his profoundly isolating, suffocatingly formalist, stomach-churning masterpiece alternately excoriated and lionized upon its release and for four decades afterward. The circumstances of Pasolini’s death, in which a young Roman hustler, who later recanted, initially confessed to running Pasolini over with the director’s car multiple times, has spawned finger-pointing conjecture rivaling the Kennedy assassination among two generations of conspiracy-minded cinema aesthetes.

In the context of a sad contemporary cultural atmosphere that tolerates repugnant and childish torture-porn entertainments such as Eli Roth’s lowbrow “Hostel” and Gaspar Noé’s highbrow “Irreversible,” Pasolini’s essential diagram of “the anarchism of power” remains a far more perverse yet infinitely more compassionate and personal work of art than anything created in its turbid, tragic, and, for better or worse, highly influential wake.