Most of the dialogue was improvised by the cast. Gaspar Noé stated that, as he didn't understand English very much, he needed someone to tell him if what the cast was saying sounded good or not.
The film's world premiere was near the end of the Cannes Film Festival 2009 because the film was not finished at this time. Around 50 graphic artists were working on finishing the film. The running time of this festival cut was 163 minutes. Because of the tight schedule, the film was screened without opening or closing credits. The film started with "Enter" and ended with "The Void."
The ambient score of the film was assembled from existing music and sound sources collected by Thomas Bangalter from Daft Punk, whom Noé really wanted to compose the film's score but couldn't because Disney already tapped Daft Punk for the soundtrack of Tron : L'Héritage (2010)' at the time.
Gaspar Noé was inspired by the famous "star gate" sequence in Stanley Kubrick's 2001 : L'Odyssée de l'espace (1968). For creating the special trippy atmosphere, the Norwegian VJ artist Glennwiz (Glenn Jacobsen) was contacted for use of one of his videos.
Gaspar Noé intended the film to be shown at 25 frames per second, rather than the 24 usually used in cinemas. The original cut is 154 minutes at 25 fps, or 161 minutes at 24 fps.