The 420 first-degree relatives of 14 patients with anorexia nervosa, 55 patients with bulimia, and 20 patients with both disorders were evaluated for the presence of psychiatric illness, using DSM-III criteria, by the family history method. The morbid risk for affective disorder in the families of the eating disorder probands was similar to that found in the families of patients with bipolar disorder; but was significantly greater than that found in the families of patients with schizophrenia or borderline personality disorder. These results add to the growing evidence that anorexia nervosa and bulimia are closely related to affective disorder.