At the time of its 1946 release, Bosley Crowther said the film leaves the viewer "confused and dissatisfied", points out that Bacall is a "dangerous looking female" ..."who still hasn't learned to act" and notes:
The Big Sleep is one of those pictures in which so many cryptic things occur amid so much involved and devious plotting that the mind becomes utterly confused. And, to make it more aggravating, the brilliant detective in the case is continuously making shrewd deductions which he stubbornly keeps to himself. What with two interlocking mysteries and a great many characters involved, the complex of blackmail and murder soon becomes a web of utter bafflement. Unfortunately, the cunning script-writers have done little to clear it at the end.
Time called the film "wakeful fare for folks who don't care what is going on, or why, so long as the talk is hard and the action harder" but insists that "the plot's crazily mystifying, nightmare blur is an asset, and only one of many"; it calls Bogart "by far the strongest" of its assets and says Hawks, "even on the chaste screen...manages to get down a good deal of the glamorous tawdriness of big-city low life, discreetly laced with hints of dope addiction, voyeurism and fornication."
1997 release of the 1945 original cut
In the late 1990s, a pre-release version—director Hawks's original cut—was found in the UCLA Film and Television Archive. That version had been released to the military to play to troops in the South Pacific. Benefactors, led by American magazine publisher Hugh Hefner, raised the money to pay for its restoration, and the original version of The Big Sleep was released in art-house cinemas in 1997 for a short exhibition run, along with a comparative documentary about the cinematic and content differences between Hawks's film noir and the Warner Brothers "movie star" version.
Film critic Roger Ebert, who included the film in his list of "Great Movies", praises the film's writing:
Working from Chandler's original words and adding spins of their own, the writers (William Faulkner, Jules Furthman and Leigh Brackett) wrote one of the most quotable of screenplays: it's unusual to find yourself laughing in a movie not because something is funny but because it's so wickedly clever.
Note that the above quote is not specific to the 1945 version but, rather, is in reference to both films. In fact, Ebert preferred the 1946 version. He stated:
The new scenes [of the 1946 version] add a charge to the film that was missing in the 1945 version; this is a case where "studio interference" was exactly the right thing. The only reason to see the earlier version is to go behind the scenes, to learn how the tone and impact of a movie can be altered with just a few scenes... As for the 1946 version that we have been watching all of these years, it is one of the great films noir, a black-and-white symphony that exactly reproduces Chandler's ability, on the page, to find a tone of voice that keeps its distance, and yet is wry and humorous and cares.
In a 1997 review, Eric Brace of The Washington Post wrote that the 1945 original had a "slightly slower pace than the one released a year later, and a touch less zingy interplay between Bogart and Bacall, but it’s still an unqualified masterpiece."
In 2003, AFI named protagonist Philip Marlowe the 32nd greatest hero in film. Empire magazine added The Big Sleep to their Masterpiece collection in the October 2007 issue.