In some ways, very different. The basic plotline of the show is followed, but only in a general way. The biggest change in the storyline is that when Ravenal abandons Magnolia in the 1951 film, their daughter Kim has not been born yet. (In the stage version and the 1936 film Kim is already a little girl when Ravenal leaves, and a grown woman when he returns. In the 1951 film, Kim is a small child when Ravenal returns.) And unlike the stage or the 1936 film version, Ravenal actually does meet Julie in a crucial new scene near the end of the film.
Another change is that the "miscegenation" scene, in which it is revealed that Julie (Ava Gardner) is part-black and therefore illegally married to her white husband (Robert Sterling), is given much less shock value than in the play or the 1936 film. This is mostly due to the fact that when Steve draws blood from Julie so that he and Julie can claim that Steve too is part-black , he pricks Julie's finger with what looks like a tiny sewing pin, rather than cutting the back of her hand with a threatening-looking pocket knife, and neither Julie nor any of the others watching react to this.
The screenplay for this film version throws out nearly all of Oscar Hammerstein II's original dialogue, which had been kept in the 1936 film. Several new scenes and conversations not by Hammerstein have been added to this film, and the order of some of the songs has been shifted - for instance, "Ol' Man River" is first sung much later here than in the original show or the 1936 film, and "Life Upon the Wicked Stage", which was played but not sung or danced in the 1936 film, is here moved to the New Year's Eve sequence in Chicago rather than sung in Mississippi, as in the original show. It is also performed as a number on a stage, rather than "in character", as in the show. The "Cakewalk", from the Act I Finale, is danced by the black levee workers in both the stage version and the 1936 film version, while in this version it is danced first by Ellie and Frank (who are white), and later by Cap'n Andy and Kim (who are also white).
The African-American chorus, which adds so much atmosphere in both the stage version and the 1936 film, does not sing or dance at all in this version, so that in this film those who would normally be members of that chorus are reduced to being simply extras. A "disembodied", offscreen chorus is heard singing instead.