Widely attacked by both the Mexican press and members of the intelligentsia, Los Olvidados (1950), directed by Luis Buñuel, is about a group of destitute children and their misfortunes in post-World-War-II Mexico City's poor and squalid slums, who steal to live and live to steal as well. Filmed at Tepeyac Studios and on location in Mexico City, the film contains elements of surrealism, although it can be judged in the tradition of social realism. When producer Óscar Dancigers initially proposed the idea for the film, Buñuel already had a script ready about a boy who sells lottery tickets. But as Dancigers intended to portray a serious depiction of children in poverty in Mexico City, Buñuel studied actual slums in Mexico City for about six months, along with the scriptwriter and theart director of the proposed film.

Finally, they came up with a script, claimed to be based on actual case study files and newspaper clippings with a few changes, which pleased Dancigers. However, upon initial release in Mexico in 1950, the film was fiercely criticised by the press, government, upper and middle class audiences, for exposing the nation's problems with poverty and crime and its theatrical commercial run only lasted for three days. Although Torres Bodet, the Mexican ambassador to France, reportedly objected to the representation of Mexican society in the film, ultimately Luis Buñuel won the Best Director award for it at the 1951 Cannes Film Festival.

Los Olvidados begins with a group of children playacting a bullfight, with a giant close-up of a boy with unkempt hair, a dirty face and crooked teeth, snorting like a bull and charging at the camera. However, the film mainlyfollows El Jaibo, a juvenile detention runaway, reuniting with those street urchins that he leads.

He enlists the wide-eyed Pedro to help him to track down Julián, the youngster who supposedly sent him to jail. Overwhelmed by his ruthlessness and knowing well that he could not escape from the grasp of his older, larger and brutal friend, Pedro took El Jaibo to the construction site where Julián worked. Before confronting Julián, El Jaibo puts his unharmed arm in a sling, hiding a rock in it. However, Julián denied his allegation of reporting him to the police and started to walk away, refusing to fight as it would not be a fair fight. El Jaibo immediately took the opportunity and heavily injured him by unethically throwing the rock from behind in the back of the head. As Julián took the ground in extreme pain, El Jaibo started to thrash him brutally till he died the shadow of a half-built high-rise building. He then took away Julián’s money, shared it with Pedro to make him an accomplice and warned him not to report the crime.

However, although Pedro was associated with Jaibo and became a witness to the murder, he was eager to change his life, he wanted nothing more than to return home and live a normal life.

Abandoned by his mother and by society, left to fend for himself at an absurdly young age, he was unable to avoid the cycle of poverty, desperation and crime. In the most famous scene in the film, he dreamt the disturbing sight of Julian’s bloody dead body under the bed, offset by the pacifying visage of his mother, who expressed her trust in his goodness and assured him to remain with him all the time. But at the same time, Pedro was wondering why she refused him any of the meat she had served to her other children. As if in reply to his thought, she smiled and walked towards him in slow motion with a rotting slab of stale meat in her hand. While she was advancing towards him, a long and distended hand emerged from beneath his bed, looking supernaturally extended as it grasped at the meat. The dream ended, when Pedro realised the hands to be of El Jaibo.

Nevertheless, the dream of Pedro is the core of his fantasies. Deep in his mind, he was aware that. Jaibo wants to possess what is rightfully his property and he preys on his vulnerability, having been an unwilling accomplice in Julian’s murder. They are the two halves of the same whole, with Jaibo the destroyer and Pedro wishes to be the constructor. Despite his desperate urge, Pedro is unable to avoid Jaibo, as he is a manifestation of his own ugliest desires. Even, Jaibo’s seduction of Pedro’s voluptuous and attractive mother can be seen as a form of oedipal seduction, an unconscious sexual desire, acting on the half-buried wish of Pedro’s dream, which Pedro can never successively avoid.

Determined to start behaving better, Pedro found the job of an apprentice to a blacksmith, only to be hounded by El Jaibo, who one day came to the workshop in the absence of others, to talk with him, and stole an ordered knife from the blacksmith's table, before he left. Although Pedro was not aware of the theft and he repeatedly denied the allegation, he was accused of the crime and sent to the farm school for juvenile rehabilitation. The judgement made Pedro frustrated as nobody believed his words and frustration made him more adamant as he got into a fight inside the farm and in retaliation, brutally killed two chickens. It was followed by the most important scene of the film, when instead of punishing Pedro, the principal of the farm school tried to fathom his psychology. To test Pedro’s integrity, the principal gave him a 50 pesos bill and asked him to out of the open doors of the farm and walk to the corner store to get a packet of cigarette for him. The offer melted Pedro’s initial hostility and made him delighted, as he was trusted, at least for the time being, and it allowed him to prove himself.

However, as Pedro struts down the street in the direction of redemption, luck betrayed him and emerging from nowhere, El Jaibo forcibly took away the 50 peso bill from him. The incident made Pedro sad, upset and angry, as it seemed to him that his attempt to be good was foiled again and he was unable to return to face the principal, as he failed in the errands. He tried to find a hiding place, but could not find any. He was desperate to find El Jaibo to settle scores and ultimately tracked him down in the cow shed of Mecha, a local girl, but only thrashed to be killed by him. When Meche and her grandfather found Pedro's body in their shed, they dumped his body down a garbage-covered cliff, as they did not want to be harassed for being involved in the matter. Ironically, on their way, they met Pedro’s mother searching for him, although she was once unconcerned with her disobedient child. However, El Jaibo could not escape his crimes and was greeted with the same fate, when he encountered the police and was shot dead.

In 1996, an alternate ending of Los Olvidados was discovered, in which El Jaibo accidentally fell from the roof of the barn, while fighting with Pedro and died. After that, Pedro retrieved the money stolen from him and returned to the reform school with the money recovered. However, it is not known whether Bunuel himself shot it or the producer had arranged someone else to shoot it, in case of any objection by the censors to the bleak ending. However, Buñuel never mentioned it in subsequent interviews or his memoirs. Nevertheless, the film marked a unique moment in Buñuel’s work, when the focus of his work shifted toward the lives of the bourgeois.