This film was the winner of the 1968 Chicago Film Festival.
J.R. (Harvey Keitel) is a typical Catholic Italian-American young man on the streets of New York City. Even as an adult, he stays close to home with a core group of friends with whom he drinks and carouses around. He gets involved with a local girl (Zina Bethune) he meets on the Staten Island Ferry, and decides he wants to get married and settle down. As their relationship deepens, he declines her offer to have sex because he thinks she is a virgin and he wants to wait rather than "spoil" her.
One day, his girlfriend tells him that she was once raped by a former boyfriend. This crushes J.R., and he rejects her and attempts to return to his old life of drinking with his friends. However, after a particularly wild party with friends, he realizes he still loves her and returns to her apartment one early morning. He awkwardly tells her that he forgives her and says that he will "marry her anyway." Upon hearing this, the girl tells him marriage would never work if her past weighs on him so much. J.R. becomes enraged and calls her a whore, but quickly recants and says he is confused by the whole situation. She tells him to go home, and he returns to the Catholic church, but finds no solace.
Martin Scorsese appears in an uncredited role as a gangster.
Who's That Knocking at My Door was filmed over the course of several years, undergoing many changes, new directions and different names along the way. The film began in 1965 as a student short film about J.R. and his do-nothing friends called Bring on the Dancing Girls. In 1967, the romance plot with Zina Bethune was introduced and spliced together with the earlier film, and the title was changed to I Call First. This version of the film received its world premiere at the Chicago International Film Festival in November 1967. Finally, in 1968, exploitation distributor Joseph Brenner offered to buy the picture and distribute it on the condition that a sex scene be added to give the film sex exploitation angles for marketing purposes. Scorsese shot and edited a technically beautiful but largely gratuitous montage of J.R. fantasizing about bedding a series of prostitutes (shot in Amsterdam, the Netherlands with a visibly older Keitel) and the film finally became Who's That Knocking at My Door (named for the song which closes the film). The film was then re-issued under the title J.R. in 1970, however all subsequent releases have been published under the 1968 title.
The film was shot with a combination of 35 mm and 16 mm cameras. Scorsese shot most of the 35 mm footage with a Mitchell BNC camera, a very cumbersome camera that impeded mobility. He opted to shoot several scenes with the 16 mm Eclair NPR camera in order to introduce greater mobility, then blow up the footage to 35 mm.
American critic Roger Ebert gave the film an extremely positive review after its world premiere at the Chicago International Film Festival in November 1967 (when it still went by the name "I Call First"). He called the film "a work that is absolutely genuine, artistically satisfying and technically comparable to the best films being made anywhere. I have no reservations in describing it as a great moment in American movies."
When the film finally received its theatrical release two years later, Ebert admitted that he had been perhaps a little over eager with his first review, admitting that "Scorsese was occasionally too obvious, and the film has serious structural flaws." However, he was still highly positive towards the film, and suggested that "It is possible that with more experience and maturity Scorsese will direct more polished, finished films."
Martin Scorsese's mother, Catherine, appears briefly as J.R.'s mother cooking at the beginning of the film and serving food near the end. Mrs. Scorsese would continue to appear in many of her son's films until her death in 1997. Scorsese himself appears uncredited as one of the gangsters. To this day, he still makes cameo appearances in many of his films.
The role of Sally Gaga is played by Michael Scala, the father of rapper Pizon.