The movie is based on a play by German playwright Rolf Hochhuth which started a lot of heated discussions and arguments after its first release in 1963. It even caused some diplomatic tensions.
The Vatican did not give a permission to shoot the film in their buildings. After searching a scenery of adequate size for the scenes taking place in the Vatican, Costa-Gavras finally chose Europe's largest building, the House of the People (Casa Poporului) in Bucharest. Some of the outdoor scenes were shot in Mogosoaia Palace, some fourteen kilometers northwest of Bucharest.