The authors describe the psychometric development of the fourth revision of the Interview for Diagnosis of Eating Disorders (IDED-IV). The IDED-IV was tested for the purpose of differential diagnosis of eating disorders, that is, anorexia nervosa, bulimia nervosa, and binge eating disorder. Evidence for internal consistency was found for symptom ratings relevant to anorexia nervosa, bulimia nervosa, and binge eating disorder. Support was found for the content validity as well as the concurrent and discriminant validity of the IDED-IV. Finally, tests of the interrater agreement for differential diagnosis of eating disorders found the IDED-IV to yield very reliable data. The authors conclude that the IDED-IV yields sufficiently reliable and valid data to be used for determining diagnoses in research studies and clinics specializing in the treatment of eating disorders.