The film was shot almost entirely in sequence; only pickups and a few reshoots were shot out of sequence.

The scene where Jim and Selena celebrate with Frank and Hannah was shot on September 11, 2001. Danny Boyle said it felt extremely strange to shoot a celebratory scene on that particular day.

For the scenes on the motorway, the production got permission to shoot on the M1 on a Sunday morning between 7.00am and 9.00am. The police gradually slowed traffic in both directions. Using 10 cameras, the filmmakers managed to capture a total of one minute of usable footage.

Athletes were cast as the Infected because of how important physicality is to them. Danny Boyle felt that since athletes can do things other people can't, they would be interesting when translated into the movements of the Infected.

Alex Garland and Danny Boyle did a great deal of research into social unrest, drawing ideas from things that had happened in Rwanda and Sierra Leone (such as the piling of bodies inside churches), but drew the line at using any actual footage from such incidents in the opening montage. All footage featuring dead bodies/desecration of bodies was faked.

The hospital in the film is a real day hospital, open only during the week. The trust managers of the hospital hire out the building to filmmakers for weekends, and the productions pay the hospital directly, meaning the money from filming goes directly to the hospital's trust fund.

Ewan McGregor was the original choice to play Jim, but he and director Danny Boyle had a falling-out at the time over The Beach (2000), in which McGregor was supposed to play the lead until he was replaced by Leonardo DiCaprio (they have since reconciled). After that didn't work out, the role was offered to Ryan Gosling, who had a scheduling conflict.

Horror novelist Stephen King bought out an entire showing of the film in New York City.

The crew filed all of the necessary papers to destroy the Canary Wharf petrol station, but the police were (unintentionally) not notified. When the explosives were detonated, police sent fire brigades (although one was already present). Danny Boyle resolved the matter after several hours. The explosion cost £250,000 total.

One of the first mainstream films to be shot entirely digitally as opposed to with film.

For the London scenes, police would close the roads at 4am, and filming would begin immediately. After 1 hour, the police would reopen the roads. The producers correctly predicted that asking drivers (including clubbers headed home) to either wait for up to an hour or find another route might make some of them angry. They got several extremely attractive young women (including Danny Boyle's daughter) to make the necessary requests, and the drivers responded quite amicably to them.

The news footage which begins the film was based on footage shot by the journalist Sorious Samura in Sierra Leone.

Alex Garland and Danny Boyle felt that the notion of the living dead wanting to eat peoples' brains was outdated. One of the original factors behind zombie movies was a fear of nuclear power and its possible effects on people. Garland and Boyle concluded that one of the biggest fears in modern society is fear of disease, especially a viral apocalypse, such as Ebola or Marburg. Garland and Boyle were specifically inspired by such incidents as anthrax and bio-terrorism scares in London and the spread of mad cow disease and foot-and-mouth disease in the UK.

The 'design' for the symptoms of Rage was based on Ebola, which is communicable in all primates (including humans), and is transmitted through the blood. Ebola is a hemorrhagic fever which leads to a rash, red eyes and both internal and external bleeding. Indeed, in 28 Days Later: The Aftermath (a graphic novel set between 28 Days Later and 28 Weeks Later (2007), it is explained that the Ebola virus was being used by the scientists as a carrier for the inhibitor which mutated into Rage.

The scene when Jim finds the money on the steps and picks it up, was based on a photograph Danny Boyle had seen of Cambodia after Pol Pot had been driven out.

The extras who played the dead bodies in the church were college students who volunteered to appear in the film.

The shot where Jim sees the dead mother holding onto her dead baby is based on a photograph Danny Boyle saw of a mass of Kurd bodies after they had been gassed.

The shot of the notice board at Piccadilly Circus, with the missing persons fliers, caused some controversy when the film was first released. Some said it was insensitive to what happened in New York after the 9/11 attacks. The film was shot prior to 9/11/01, although it was released afterward. Danny Boyle said he based the shot on a photograph he saw from an earthquake in China. He also said that if he'd made the movie after the 9/11 attacks, he wouldn't have shot that scene.

Cillian Murphy's nude scenes were done on a closed set, at Murphy's insistence.

All of the mansion scenes that involved upstairs rooms were filmed downstairs because the mansion's owner lives upstairs. When Jim jumps through the window in the roof, he is actually jumping through a hole in the corridor upstairs down to the ground floor.

The tower block where Hannah and her father lived is Belfron Tower which has been converted into luxury flats

The symbol used for this film is the international symbol for blood-borne biohazard.

The decision to film on DV (using Canon XL1 cameras) was both an aesthetic and a logistic choice. Aesthetically, Danny Boyle felt that the harshness of the DV imagery suited the post-apocalyptic urban landscape and the grittiness of the film in general. In the production notes, Boyle says "the general idea was to try and shoot as though we were survivors too." Logistically, producer Andrew Macdonald claims that shooting with standard cameras, especially some exterior scenes, would've been impossible. As MacDonald points out in the production notes, "The police and the local authorities were quite happy to assist us because we could set up scenes so quickly. We could literally be ready to shoot with a six-camera set-up within minutes - something we would not realistically have been able to do if shooting under the restrictions of 35mm which takes a good deal more time to set up a single shot."

The scene where Jim, Selena and Mark shelter from the explosion by hiding between the windows was based upon a photo Danny Boyle had seen of a bomb blast in Northern Ireland.

Stephen King is a huge fan of the movie and paraphrases one of Selena's lines in his novel, "Doctor Sleep", "He needs us more than we need him".

The tunnel scene was filmed in a new tunnel extension which the filmmakers had special permission to use.

The film includes heavy product placement for Britain's National Lottery, which funds the British Film Council.

The tunnel sequence took two days to shoot.

The Bible verse on Jim's postcard is from the Book of Nahum. Nahum was a prophet who predicted the destruction of the great city of Nineveh, the capital of the Assyrian empire. It was to be utterly destroyed as a punishment for its inhabitants' sins.

The flashback scenes of Jim's parents were shot on Super 8mm film.

Included among the "1,001 Movies You Must See Before You Die" edited by Steven Schneider.

Although unconfirmed, the title may refer to the fact that peak immunity from a virus is widely considered to occur 28 days after an infection is contracted.

Cillian Murphy was suggested to Danny Boyle for the role of Jim by Paloma Baeza, who had acted opposite him in Sunburn (1999) and The Way We Live Now (2001), playing his love interest in both productions. She would appear as his sister in Danny Boyle's Sunshine (2007).

Danny Boyle intentionally sought out unknown and obscure actors for the majority of the leading roles, as he wanted the film to be discovered and not rely solely on star power. Cillian Murphy, Naomie Harris, Noah Huntley, and Megan Burns were virtually unknown prior to the film production, with Murphy and Huntley having only had minor roles in films, Harris only having done British television, and Burns having only had one previous acting credit. The only famous actors of note that were cast were Brendan Gleason and Christopher Eccleston.

Jim, Selena, Mark, Frank, and Hannah's surnames are never revealed during the film or in the end credits. Likewise, Jim's parents names are never revealed.

The angelic song that plays in the background, particularly during the car trip, is Gabriel Fauré's "In Paradisum".

The single malt whisky that Frank is discussing with Jim in the supermarket is from the Lagavulin distillery. The whisky is part of the Classic Malts series and is known to be one of the smokiest and peatiest scotch whisky around. Frank appears to be a connoisseur considering his comments on the whisky when he says "peaty aftertaste" and "takes out the fire but leaves in the warmth".

If you actually traveled 27 miles northeast of Manchester, you would end up in Huddersfield, West Yorkshire.

The film's famous climactic score 'In the House - In a Heartbeat' by John Murphy was used in the sequel 28 Weeks Later (2007) and later in various films and trailers, for example for the films, I Know Who Killed Me (2007), Kick-Ass (2010) (for which Murphy also wrote the score), the trailer of the video game Metro 2033 (2010) and a Louis Vuitton commercial in 2012.

A scene that was shot and later abandoned involved a taxicab full of people singing The White Stripes' "Hotel Yorba".

The word "fuck" is used 61 times.

Megan Burns retired from acting after appearing in this film, not wishing to pursue a full-time career as an actress, and instead focused on her passion for music and singing. She would not do another film for 16 years until she was cast in In2ruders (2018)

Megan Burns only had one previous film credit prior to this film, in Liam (2001) as Teresa. Danny Boyle selected her for the role of Hannah based on the strength of her performance in that film. She was his first and only choice.

The movie is spoofed in the music video to LMFAO's "Party Rock Anthem".

Cillian Murphy would go on to star in the sci-fi thriller, Sunshine (2007), along side Rose Byrne who had starred in 28 Weeks Later (2007), the sequel to this movie.

This is director Danny Boyle's fifth film.

Danny Boyle: [bridge] Jim is briefly seen crossing a large bridge.

Danny Boyle and Naomie Harris developed a back-story to explain Selena's hard-nosed, ruthlessly pragmatic outlook. Apparently, Selena was forced to kill her infected mother and father to save her baby brother, only to discover that her brother was also infected.

The scene when Major West reveals his plans for Hannah and Selena to Jim was written by Cillian Murphy, Christopher Eccleston, and Alex Garland the night before it was shot. A different scene had been scripted and shot, but no one was happy with it, especially the two actors.

In the end of the film, the pilot of the plane is speaking Finnish on the radio. The very last words he says are, "Lähetätkö helikopterin?" which means "Will you send a helicopter?"

Another aspect of rendering the zombie movie more contemporary was the idea that the virus didn't necessarily affect people physically (it doesn't kill them as in traditional zombie movies), but psychologically. Both Alex Garland and Danny Boyle felt that the idea that the virus renders people zombie-like due to uncontrollable rage was a good metaphor for the contemporary phenomenon of social rage (such as road rage, air rage, hospital rage, etc). They liked the idea that the virus simply amplifies something already in each and every man and woman, rather than turning them into something entirely Other, as is the traditional route in zombie movies.

The execution pit scene near the end was filmed outside a church off Witherington Road, connecting Salisbury to Downton. One of the prop teams didn't pick up the fake bodies after filming. A local hairdresser from Downton saw them from the road, panicked, crashed her car, and phoned the police, who came to investigate and interrogate the crew.

Danny Boyle explains on the DVD commentary that he shot all the scenes of the Infected in a particular style - using a type of slow motion feature on the Canon XL1 DV cameras with which the film was shot. Boyle explains that the cameras allow filming at up to 1600fps (normal speed is 24/25fps), but that shooting at such a high speed on a DV camera doesn't produce the same effect as it would on a 35mm camera. Shooting at that speed on a film camera gives basic slow motion, but doing so on a DV camera produces the kind of staccato effect seen in scenes involving the Infected. As Boyle explains it, it almost looks as if every third or fourth frame is trimmed insofar as the image has a 'jumpy' quality. Boyle also explains that during the climax of the film, as Jim runs around the mansion, all the scenes involving Cillian Murphy were shot in the same way - thus setting up for the audience a psychological parallel between Jim and the Infected.

The film has engendered some confusion as to whether or not the virus is a worldwide phenomenon or whether it's confined to Britain. This is clarified on the DVD commentary, however. When shooting began, Danny Boyle and Alex Garland intended to reveal that the virus had spread worldwide, which is why Selena mentions outbreaks in Paris and New York early in the movie. However, as filming progressed, they changed their minds and decided to render the spread of the virus more ambiguous. As such, they wrote the dialogue spoken by Sergeant Farrell (Stuart McQuarrie) when he is tied to the radiator as a counter-theory to Selena's claims; he hypothesizes that Britain would have simply been quarantined at the first sign of trouble and that there was no way the virus could have reached America or mainland Europe. Obviously, the sequel 28 Weeks Later (2007) confirms that Farrell was entirely correct.

In the script, it is Jim, instead of Selena, who has the last line: "Do you think he saw us this time?"

Several endings were filmed, including a few in which Jim (Cillian Murphy) is taken to a hospital where he succumbs to his gunshot wound, despite efforts by Selena to revive him. Selena and Hannah subsequently leave the hospital together, an open ending that was meant to suggest that they would make it. However, a test audience interpreted this as a sign of certain death for them, so the makers filmed a special epilogue with a more uplifting ending.

When Jim escapes from the two soldiers who are about to execute him, the shots of the jet flying overheard were shot by director Danny Boyle. During filming, Boyle took one of the Canon XL1's home, and spent 2 days filming planes through the trees in his backyard.

Robert Carlyle was offered the role of Major Henry West. Ironically, he would play an antagonistic role as the infected Don in the sequel 28 Weeks Later.

While filming the mansion scenes, the crew spent a lot of time at the Wooden Spoon in Downton, Wiltshire. They liked it so much that they gave the pub one of the dead bodies from the execution pile. The pub now has new owners.

Christopher Eccleston and the other soldiers in the film did a three-day training program with real soldiers to help them learn how to carry themselves believably.

Shortly after Mark dies, when Jim and Selena left Jim's parent's house, they are seen walking past three broken clocks outside a building, where the clock in the middle had the second's arm stuck in 28th second.

Scriptwriter Alex Garland acknowledges several sources as inspiration for his screenplay, notably John Wyndham's Invasion of the Triffids (1963), George A. Romero's "Dead" trilogy (Night, Dawn and Day) and The Omega Man (1971). Direct homages include Jim waking up in the hospital from Invasion of the Triffids (1963), the chained infected being studied from Day of the Dead (1985), and the scene in the grocery store (people in the mall from Dawn of the Dead (1978)), the stop for supplies that saw a run-in with infected children (also Dawn of the Dead (1978)), and the military holing up against the plague with outsiders partially to deliberately include females (also Day of the Dead).

When Jim, Selena and Hannah first enter the manor where the soldiers have set up their fortress, a Roman statue of the Laöcoon group can be seen in the centre. In Virgil, Laöcoon was a Trojan priest who was attacked by giant serpents sent by the gods, and his most famous line is "Do not trust the Horse, Trojans / Whatever it is, I fear the Greeks even bearing gifts." His appearance is significant because he foreshadows the soldier's betrayal and ulterior motives.

The plane used in the film flew from Blackpool to the location in the lakes. It took the crew hours to make the same journey, but it took the pilot less than four minutes and cost £6,000 in fuel.

Prominently featured in the soldiers' mansion is a statue of Laocoon, the Trojan priest who attempted (in vain) to warn his countrymen that they had something to fear from the horse, just as Jim, Selena, and Hannah have something to fear from the soldiers.

The last scene (the scene at the cottage in the lakes) was shot in standard 35mm.

Jim (Cillian Murphy) spends thirty percent of the film shirtless and nude.

Some argue that the story draws heavily from and even follows the basic storyline of The Day of the Triffids; for example the main protagonist escaping the disaster by being incapacitated in hospital, a deserted Britain, a group of people leaving London for a better place and even the 'escape from the soldiers gone bad' scenario towards the end.

Though the film has scenes of zombies attacking people by biting and maiming them, ironically, the most gruesome scene in the entire film is Jim killing the would-be rapist soldier by beating him up and gouging his eyes out.

The way Jim was shown attacking and killing the would-be-rapist soldier mirrors the attacks of the zombies infected with the Rage Virus. This scene symbolizes Jim's righteous rage at that point.

There is one specific connecting factor between the prologue and the epilogue: the pilot of the plane at the end speaks perfect Finnish (very hard for people of different mother tongue), whereas one of the Activists (the male follower) in the beginning speaks English with a distinctive, thick Finnish accent, confirming his mother tongue. He's also played by a Finnish actor, Jukka Hiltunen.

The jet plane in the last scene is a British made Hawker Hunter.

Body Count: 14 (possibly more)

Other filming locations exist that for some reason were not published. As the group arrive at the army blockade you can clearly see a motorway sign that says A6 Preston and Garstang and the one next to it says M6 South Manchester and Birmingham. The only place this is at is on the M6 J32 southbound from Lancaster at the Preston interchange where the motorway M55 junction is on the M6. Also when Jim escapes the army compound and alerts the sirens directly behind his head while he is turning the siren it says M55 Blackpool and Fleetwood. It would be approximately around the Broughton area of the M6 at the north of Preston.