For many years Freud treated a woman patient who meant very much to him and for whose treatment he made the most extraordinary sacrifices. He wrote down her case history, and he described her case in at least six articles. In addition, this woman played a major role in the conflict between Freud and Jung. This paper sketches the case history, presents Freud's interpretation of her neurosis, and outlines the important consequences of this classical case in the history of psychoanalysis for theory and technique.