text: The casting of Fernando Rey as the main French heroin smuggler, Alain Charnier (irreverently referred to throughout the film as "Frog One"), resulted from mistaken identity. Friedkin had seen Luis Buñuel's 1967 French film Belle de Jour and had been impressed by the performance of Francisco Rabal, who had a small role in the film. However, Friedkin did not know his name, and remembered only that he was a Spanish actor. He asked his casting director to find the actor, and the casting director instead contacted Rey, a Spanish actor who had appeared in several other films directed by Buñuel. After Rabal was finally reached, they discovered he spoke neither French nor English, and Rey was kept in the film.
  Comparison to actual people and events
  The plot centers on drug smuggling in the 1960s and early 1970s, when most of the heroin illegally imported into the East Coast came to the United States through France (see French Connection).
  On April 26, 1968, a record-setting seizure of  of heroin was made, concealed in a Citroën DS and smuggled to New York on the  ocean liner. The total amount smuggled during the many transatlantic voyages of this DS was  according to arrested smuggler Jacques Bousquet.
  In addition to the two main protagonists, several of the fictional characters depicted in the film also have real-life counterparts. The Alain Charnier character is based upon Jean Jehan, who was arrested later in Paris for drug trafficking, though he was not extradited since France does not extradite its citizens. Sal Boca is based on Pasquale "Patsy" Fuca, and his brother Anthony. Angie Boca is based on Patsy's wife Barbara, who later wrote a book with Robin Moore detailing her life with Patsy. The Fucas and their uncle were part of a heroin-dealing crew that worked with some of the New York City crime families.