The character of Eddie Ryan (Robert Duvall) is loosely based on real-life New York City cop Eddie Egan, who was the detective who busted "The French Connection". Egan was fictionalized as Jimmy "Popeye" Doyle, and played by Gene Hackman in the movie based on Robin Moore's book detailing his most famous case, The French Connection (1971). Some display ads for this movie ran with the tagline: "Based on the exploits of Eddie Egan--the cop with French Connections".
The bus chase sequence at night took almost two weeks to film.
The picture was shot entirely on-location in New York City, and utilized a total of fifty-three locations.
Eddie Egan, on whom Eddie Ryan (Robert Duvall) was based, appeared in the movie, playing Lieutenant Scanlon, the superior of "Eddie Ryan". Egan also acted as a technical consultant on the film.
Johnny Pacheco & His Orchestra: The Dominican musician and band leader Johnny Pacheco & His Orchestra as a band at Carorrojeno's during the film's opening sequence.