Charles Boyer often fought with Max Ophüls about his character's motives. Ophüls one day during rehearsal broke down and said "Enough! His motives are he is written that way!" Boyer never asked him again and decided to play his character as being omnipotent in all his scenes.
Vittorio De Sica was a huge fan of Max Ophüls and wanted Jean Gabin's role in Pläsier (1952). Ophüls told him no, but that he would find him a dignifying role in another film. The role of the Baron was written with him in mind for this film.
Louise de Vilmorin chose to keep her characters nameless in order to match the style of Belle Époque authors, who employed the technique in order to make it seem as if their characters were based on real people. Max Ophüls decided to keep the characters surnames a secret in the film adaptation, because he felt that it created the suggestion that his characters could represent anybody from the story's milieu.
The movie most likely takes place in 1880, for at one point the general mentions that he and the countess are off to see Sarah Bernhardt in the play Adrienne Lecouvreur--a role that Bernhardt adopted only in 1880 before leaving for a long tour of the US. He had also mentioned earlier that his wife had fainted for 20 minutes during the Lisbon earthquake--almost certainly a reference to the 1880 quake (estimated at 6.1 on the Richter scale) (The most recent earlier significant Lisbon quake had been in 1856, and the next one not until the early 1900s).
The film was reportedly the all time favorite of fellow director Stanley Kubrick.