Filming started on 14 June 1982 and ended on 22 Apr 1983.  At that time Leone had ten hours of useable footage.  With help from editor Nino Baragli, this was pruned to six hours.  Finally accepting that there was unlikely to be a two-part version, Leone delivered a fine cut of three hours and forty-nine minutes.  His ideal running time would have been between four hours ten minutes and four hours twenty-five minutes but he relucatantly excised between forty-five and fifty minutes worth of significant material.

From April 1983 onwards there had been rumblings from the Ladd Company, the American distributor, that the film would require cuts to bring it close to the 165 minutes that Leone had been contracted to deliver.  The Ladd Company was still reeling from the disaster on the American market of "The Right Stuff" which ran for a mere three hours and fourteen minutes and Robert De Niro had not appeared in a profit-making project since "The Deer Hunter" five years earlier.

On 17 February 1984 a sneak preview in Boston of a 227 minute version confirmed the distributor's worst fears.  The audience's reaction was "confused", "angry", "too long".  At Cannes on 20 May 1984 where the movie was shown in its three hour forty-nine minute version, it received acclaim from many critics.

Leone retained lawyers in an attempt to preserve his work but the Ladd Company instructed Zach Staenburg to re-edit the film.   Staenburg's version lasted 144 minutes, jettisoned the flashblacks and some of the gang's childhood escapades, began with Deborah's dance in 1923, had characters cropping up without explanation and ended with the sound of a gunshot as Bailey unambiguously committed suicide.  An executive of the Ladd Company claimed that a screening of this new version has played infinitely better than the Boston screening and the truncated version opened in America on 1 June 1984.

The film flopped and a 227 minute version was released in Europe with mixed success.  This was followed by releases on VHS and other formats.

In June 2003, 220 & 229 minute DVD versions (PAL/NTSC) were released by Warner Bros and in 2011 they issued a Blu-ray with a running time of 229 minutes. Although some parts are not pin sharp, it was at the time generally considered to the best available version of the movie.

Additional unreleased scenes have been known about since the early nineties and are mentioned in Oreste De Fornari's 1997 book on Sergio Leone.
In 2000, Film4 released a documentary "Once Upon a Time: Sergio Leone". This included teasing images of 6 film reel cans labelled "Cemetery - Louise Fletcher", "McGovern - Shakespeare scene", "Eve out takes" and Arnon Milchan saying: "There's another half hour we're planning to put back and come with a full director's version. This time I know what to do."

At an interview with Raffaella Leone in 2006 she mentioned 40 minutes of unpublished material they had found and a planned restoration with Sky. At that time she was against the additional scenes being incorporated into her father's film and wanted the additional scenes to be shown separately at film festivals.

In mid 2011 Andrea Leone acquired the Italian rights from Arnon Milchan saying that his father had made a version of four and a half hours (270 minutes), which was cut in Europe to three hours and forty (220 minutes). The 50 minutes of cuts included "une scène d'amour avec Deborah petite fille" - a scene of love with young Deborah and it is thought that for the Europen release, Leone put this back into the movie bringing the running time to 227 to 229 minutes.

In May 2012 it was announced that an extended and restored version of the movie would be shown at Cannes and details of the six blocks of additional scenes with a total running time of 26 minutes were given.  However adding the running times of the additional scened together results in a total of 22 mins 34 secs only.

Shortly after Cannes
, an extended version with a running time of 251 minutes was released in Italy on Blu-ray and other formats and in 2014 similarly extended versions were released in the U.S. Whilst slightly sharper than WB's 2011 BD, they have a yellowish tint and despite extensive restoration work, the quality of some of the additional scenes is poor.

There are obviously another 20 minutes or so from Leone's original 270 minute version which have not yet been released to the public. There may be quality or copyright issues or the scenes may conflict with other parts of the movie.  Hopefully however we will get to see them one day.