We studied hypothalamic-pituitary-adrenal-cortical (HPA) activity in nine underweight women with anorexia nervosa, 12 women of normal body weight with bulimia, and nine control subjects. The measures of HPA activity were the pattern of plasma cortisol secretion over 24 hr and the responses of plasma cortisol to dexamethasone suppression and to low dose ACTH stimulation. The patients with anorexia nervosa had significantly elevated 24 hr concentrations of plasma cortisol compared to the controls and showed significantly less cortisol suppression following dexamethasone. There was no difference between patients with anorexia nervosa and controls in the rise in plasma cortisol following ACTH. On most measures of HPA activity, the normal weight patients with bulimia were indistinguishable from the controls. These results suggest that HPA activity is normal in most patients of normal body weight with bulimia and that the psychological and behavioral disturbances common to both anorexia nervosa and bulimia are, in the absence of significant weight loss, insufficient to produce major alterations in HPA activity.