This film is based on the real-life relationship between director Jean Eustache and actress Françoise Lebrun (who plays Veronika). The character based on her is named Gilberte in the movie and is played by Isabelle Weingarten.
Jean Eustache was adamant about the actors following the script without changing a word. Because of this, Jean-Pierre Léaud spent three months memorizing his lines before the start of filming.
Not a word in the film was improvised by actors. Jean Eustache declared he knew the script by heart. Françoise Lebrun who has a long monologue, had the script on her lap just in case. She didn't need it as there was only one take.