Shirley Clarke's savagely realistic yet poetic study of Harlem youth and slum life in New York City's black ghetto was based on the novel “The Cool World” by Warren Miller, and on the play of the same name by Miller and Robert Rossen, but as a Newsweek critic pointed out, “its structure as fiction is of rather minor importance... The power of the film is in Miss Clarke's vision of Harlem, and the manner in which she uses that vision is the purest kind of moviemaking. This is not a series of squalid 35mm picture postcards, but a work of art informed by knowing compassion.... The authenticity of the dialogue was the great virtue of the Warren Miller novel. (Screenwriters) Clarke and (Carl) Lee (son of Canada Lee) have honed it even finer, and its effect in a film is vastly more powerful.”
Certainly much of the realism and documentary style of the film is due to the location shooting and casting of non-professional adolescent actors who were really street gang kids. Casting director Carl Lee tested about 2000 children from whom 40 were selected for the finished film. A method of improvisation was used for the casting and even some of the actual shooting. The Cool World stands today as a classic of the social realist cinema.