Actress Gena Rowlands once said of her ex-gun moll character: "When I read the script, I knew I wanted a walk for her. I wanted something that, from the minute you saw me, you knew I could handle myself on the streets of New York. So I started thinking about when I lived in New York, how different I walked down the street when there was nobody but me. It was a walk that said, they'd better watch out."
John Cassavetes wrote a sequel in the late 1980s entitled "Gloria 2." It was briefly mentioned in a Chicago Tribune article published on 28th February 1989, 25 days after his death, that Gena Rowlands would appear in the film, but it never got made.
John Cassavetes rounded up actual gangsters and various criminals for the scene in Tony Tanzini (Basilio Franchina)'s apartment. Cassavetes solicited their opinions about the realism of the scene. One professional hit man got into an argument with Cassavetes about how the scene would have really taken place if he were in that situation.
Star Gena Rowlands stayed in character between takes with Juan Adames (aka John Adames) so it would not interfere with the dynamic between their characters.
John Cassavetes once described the film as "a very fast-moving, thoughtless piece about gangsters - and I don't even know any gangsters."