Sir Dirk Bogarde considered retiring from acting after making this movie, which he found to be a draining experience.
According to writer and director Liliana Cavani, Charlotte Rampling (Lucia) declined doing another take of a fight scene between her and Sir Dirk Bogarde (Max) because many of the blows he threw were real.
Sir Dirk Bogarde had a very dark experience during filming. One scene shot in Austria, where the actor said, "they were much more Nazi than even the Germans were," required him to make an entrance wearing an SS uniform, cross the street and get into a car. He said he was "shit-scared" appearing in public that way. He kept hidden in an elderly woman's flat until the signal was given for him to emerge. Doffing an overcoat that covered the uniform and slipping on his black gloves, he was taken aback when the old woman fell to her knees, caressing his boots and exclaiming, "It's the good days again." The scene outside was no less disturbing. "There was an enormous crowd and, when I came out, it was like I was Garbo or Dietrich," Bogarde said. "They were shrieking with joy and singing the 'Horst Wessel Song' [one of the Nazi anthems banned after the war]. All the kids came running after me, to hold my hand, to touch the uniform---all of them."
According to an interview given by Charlotte Rampling on the National Public Radio program "Fresh Air," the scene where she dances and sings topless in a Nazi outfit was the first scene filmed.
Thanks to his critically acclaimed work in such films as Joseph Losey's O Criado (1963) and two by Luchino Visconti, Os Deuses Malditos (1969) and Morte em Veneza (1971), Sir Dirk Bogarde had become somewhat typecast and took some time off, refusing scripts that would cast him in stories of decadence, degeneracy, or Nazism. However, after viewing with much pleasure Liliana Cavani's TV film Galileo (1968) at his home in France, he remembered he had a script from her for O Porteiro da Noite (1974) down in his cellar. He then retrieved the script and read through it that night. He was attracted to the central relationship between the porter and the camp survivor, especially after he discovered the script was based on real events. He called Cavani the next morning to accept the part.