The concept of imperviousness in the ontogeny and progression of anorexia nervosa is explored in relation to a patient in her 30s, with longstanding and severe anorexia. Katie's history is traced from the early years, through adolescence into adulthood and the ensuing therapy. The relevance of lack of containment in setting up a ‘no-entry’ defence is considered in relation to the pervasive imperviousness displayed in anorexia. Some ideas derived from psychoanalytic and other clinical literature are discussed in relation to anorexia nervosa.