Norepinephrine and its metabolites were studied in various body fluids (plasma, urine and cerebrospinal fluid) of patients with anorexia nervosa, bulimia nervosa and healthy young women. The reaction of plasma norepinephrine to different stimuli like orthostatic challenge, test meals, standardized exercise, mental challenge tests etc. were studied. All results indicate a reduced noradrenergic activity in the central and peripheral nervous system of patients with eating disorders. The clinical consequences of these changes are hypotension, bradicardia, hypothermia and depression. Evidence is presented that the reduced activity of the sympathetic nervous system is caused by starvation (anorexia nervosa) or intermittent dieting (bulimia nervosa).