As a director, he favors stories showing the interrelationships between several characters; Altman states that he is more interested in character motivation than in intricate plots. As such, he tends to sketch out a film's basic plot, referring to the screenplay as a "blueprint" for action, and allowing his actors to improvise dialogue.
He frequently allows the characters to talk over each other in such a way that it's impossible to make out what each of them are saying. He notes on the DVD commentary of McCabe & Mrs. Miller that he lets the dialogue overlap, as well as leaving some things in the plot for the audience to infer, because he wants the audience to pay attention. Similarly, he tries to have his films rated R (by the MPAA rating system) so as to keep children out of his audience--he does not believe children have the patience his films require. Such a tendency sometimes spawns conflict with movie studios, who do want the children in the audience because of the size of the demographic.
His films M*A*S*H and Nashville have been selected for preservation in the United States National Film Registry.