John Waters' third feature was made in 1972 but was not formally submitted to the BBFC for classification until 1989. This was presumably because the film's contents led distributors to believe the BBFC would be unable to classify it without significant cuts. Given that the whole point of Pink Flamingos is excess, this was not an attractive or commercial option. Nonetheless, the film did enjoy occasional screenings in members-only cinema clubs during the 1970s and 1980s, notably at the Scala Cinema in King's Cross, London. The film was also released, uncut, on VHS in the early 1980s, without a BBFC classification.

Although the film was never placed on the Director of Public Prosecutions' list of potentially obscene 'video nasties', a single tape was seized in the mid-1980s, leading to a conviction under section 3 of the Obscene Publications Act. The lack of other convictions is probably accounted for by the innovative way in which the video was distributed, with customers sending a blank VHS to the distributor, onto which the film would be recorded and sent back to them with accompanying packaging.

The plot of Pink Flamingos is unusual but fairly straightforward. Babs Johnson (played by the actor 'Divine') and her family are the proud holders of the title 'The Filthiest People Alive'. Babs lives in a trailer with her egg-obsessed mother Miss Edie, her perverted chicken-loving son Crackers, and her voyeuristic 'travelling companion' Cotton. However, suburban couple Connie and Raymond Marbles are intent on wrestling the 'filthiest people alive' title from the Johnson clan. They claim to have attained a far greater degree of 'filthiness' through their business activities, which include kidnapping women, having them artificially inseminated by their butler Channing, and then selling the babies to lesbian couples. They use the money they raise to fund porn shops and a business selling heroin to school children. What ensues is a comic but also disgusting series of set pieces in which the two families strive to outdo one another, culminating in a notorious sequence in which Divine eats real dog excrement.

When the film was first submitted to the BBFC for video release, in December 1989, examiners were divided about what to do with it. The only thing on which most examiners could agree was that the video could not be passed at 18 uncut. Several examiners felt the film should be rejected, in part because cutting the most offensive moments would remove the entire point of the film, whereas others felt cuts should at least be offered to the distributor. A single examiner suggested that, although disgusting and disturbing, the film should be passed uncut. At an examiners' meeting on 23 February 1990, a vote was taken, with a slight majority in favour of attempting cuts.

As a result, James Ferman produced a 'trial cut' of the film himself. This cut version of the film was shown to the BBFC's President and Vice President, with James Ferman noting: "Presidential tier all found cut version acceptable for '18'. The Presidents saw all the cut scenes [...] both uncut and cut and agreed not to restore any of the cut material". In the end, 3 minutes 4 seconds of material was cut, from five individual scenes. Firstly, cuts were made to remove the sight of chickens being roughly handled and killed during a bizarre sexual assault on a woman; secondly, cuts were made to reduce a scene in which Channing the butler masturbates over a captive woman and injects semen into her vagina with a syringe; thirdly, cuts were made to reduce a scene in which a man flexes his anus in close up, making it look as if the anus is 'singing'; fourthly, cuts were made to remove all sight of Babs fellating her son in explicit detail; fifthly, cuts were made to remove sight of Babs eating real dog excrement. The cuts were justified on a variety of grounds, including sexual violence, degradation, animal cruelty, and obscenity. The cut version of the film was classified 18 for video release on 31 December 1990.

Pink Flamingos next returned to the BBFC in 1997 when a fresh distributor proposed re-releasing the film in cinemas, in order to celebrate its 25th anniversary. Rather optimistically, the distributor accompanied the submission with a covering letter, hoping that it would be now possible to pass the film uncut. On this occasion, examiners suggested that the previous cuts to the 'singing anus' scene could be waived, because it was essentially a matter of taste and offensiveness rather than something genuinely harmful or illegal. Particularly in the context of a limited cinema release of a notorious film at 18, this cut seemed unnecessary. The BBFC's Director, James Ferman, agreed with this course of action. Following consultation with the Presidents, the 'singing anus' cut was waived, although the cuts made to the four other scenes were upheld. In total, two minutes 42 seconds were cut for cinema release and the film was passed 18 on 27 June 1997.

Later that year, the same distributor submitted the film for video release, in the expectation that the 'singing anus' cut could now be waived for video release as well. Examiners agreed that the 'singing anus' cut could be waived, as it had been on film earlier in the year, but this time they also suggested that the scene in which Divine eats dog excrement might also be a matter of taste and offensiveness rather than harm. By this stage, the BBFC had taken on a new President, Andreas Whittam Smith.

The new President accepted the argument that the 'excrement' scene was not likely to be considered obscene in context, because of its lack of sexual motivation. Essentially it was simply a moment of bad taste 'gross out' humour and he concurred that there was a key difference between scenes that might raise legal or harm concerns and scenes that were simply revolting.

Accordingly, Pink Flamingos was classified 18 for video release in January 1999, after two minutes and 8 seconds of cuts. Only three sequences were now subject to compulsory cuts - the chicken scene, the masturbation and insemination scene, and the fellatio scene.

Pink Flamingos returned to the BBFC in 2008, for a proposed DVD release. Since its previous submission, a number of changes had occurred in BBFC policy and in the surrounding legal context. For a start, the BBFC now operated under published Classification Guidelines, the result of widespread public consultation. Those public consultation exercises had made it clear that the public did not expect the BBFC to intervene at the adult level unless such intervention could be clearly justified, chiefly on grounds of harm or legality. Furthermore, the Human Rights Act 1998 had now incorporated the European Convention on Human Rights into UK law, enshrining a basic right to freedom of expression, subject to certain constraints, and placing a requirement on the BBFC to be proportionate in its intervention. Finally, the BBFC's Guidelines, policy and practice had changed so as to permit explicit sight of real sexual activity at R18 and to allow explicit sight of real sexual activity, provided it was justified by context, at 18. At the time of Pink Flamingos' previous classification, explicit real sex was not generally permitted, even in R18 pornography.

Looking at the film again, in the light of the changes that had occurred at the BBFC and in society over the last ten years, it was concluded that Pink Flamingos could now be passed 18 uncut, 36 years after it was created. In terms of the scenes cut in 1997-99, the brief explicit fellatio could be justified by the wider context of the film, in that the whole purpose of the film was to shock, disgust and amuse (in a blackly comic fashion), rather than to arouse, and the explicitness of the image was important in creating the film's effect. The scene showing a man masturbating and injecting semen into a woman's vagina was similarly grotesque and repulsive, rather than erotic. Although the Board had previously expressed concerns about the non-consensual nature of the scene, the datedness of the film and the lack of credibility of the scene, argued against intervention.

Probably the most difficult scene was the one featuring a man 'assaulting' a woman with live chickens. However, a careful viewing of the scene suggested that the handling of the chickens, although rough, was no stronger than other scenes of animals being manhandled that had been passed in other films, such as Even Dwarfs Started Small or 1900. Furthermore, although the chickens were killed, the killing was quick and clean and therefore not in breach of BBFC policy on animal cruelty. With regard to the sexual violence in the scene, the BBFC's conclusion was that the scene was so over-the-top and so divorced from reality, that the likely response was disgust, shock and horror, rather than arousal. The BBFC, therefore, informed the film's distributor that Pink Flamingos could now, finally, be classified 18 uncut. However, the distributor subsequently chose to withdraw this submission from the classification process before a formal certificate could be issued. Therefore, the cut version remained the only version available in the UK, in spite of the BBFC's willingness to permit the film uncut in 2008.

In April 2022, the film was submitted once again for a home media release. In line with the Board of Classification’s decision 14 years previously, the film was passed 18 uncut.