The production was staffed by an Italian crew because of former Chicago Mayor Richard J. Daley denying Hollywood production staff from filming within the city.
Isaac Hayes' instrumental "Hung Up on My Baby" is heard in the film twice - once in Lee's apartment, and during the final showdown with Snake. This instrumental piece has been sampled by Geto Boys for their hit single "Mind Playing Trick on Me" in 1991.
Italian censorship visa # 64625 delivered on 16 May 1974.
Although only famous for Isaac Hayes, who also composed, he is the co-star of the movie, second to Lino Ventura, who is even ahead in the credits. This is actually Lino's movie with Hayes as the token good-cop who helps out. But Isaac doesn't enter into the story until the 25:00 mark.