Low self-esteem occurs commonly in patients with an eating disorder, a term which includes patients with both anorexia nervosa and bulimia nervosa. In this hypothesis it is proposed that chronic low self-esteem is a necessary prerequisite to the development of an eating disorder, and that chronic low self-esteem is the final common pathway through which the multiple aetiological factors involved in the causation of eating disorders act. Thus, eating disorders can best be viewed as a 'symptom' of chronic low self-esteem. This hypothesis is able to account for the recent increase in the incidence of eating disorders, and the increased incidence of depression in eating disordered patients. Suggestions for research to test this hypothesis are made.