Evidence of both blunted and enhanced cortisol suppression with the dexamethasone test (DST) is available in eating disorders (ED), suggesting that different subtypes of ED might be characterized by distinct neurobiological stress response dysfunctions. Other evidence indicates that ED patients with impulsive clinical features might have enhanced cortisol suppression similar to patients with impulsive personality disorders. A group of 52 patients with restrictive anorexia, binge eating-purging anorexia and bulimia nervosa were studied with a very low dose (0.25 mg) dexamethasone test and measures of phenomenology, personality and impulsivity. Patients with bulimic symptoms had significantly higher rates of cortisol suppression than controls and than restrictive anorectic patients. Percent cortisol suppression showed a strong and significant correlation with the patient's score on the Barratt Impulsiveness Scale. A hypersensitive cortisol response to dexamethasone, which might reflect hypothalamic-pituitary-adrenal axis dysfunctions might be specifically associated with impulsive subtypes of eating disorders.