Patients with anorexia nervosa have disturbances of mood, appetite, and neuroendocrine function. Central nervous system monoamine pathways modulate these systems, and alterations in function of these systems may occur in anorexia nervosa. Because monoamine metabolism can be influenced by nutritional intake, we studied anorectics before and at intervals after correction of weight loss. Underweight anorectics had a 30% decrease in CSF homovanillic acid level and a 20% decrease in CSF 5-hydroxyindoleacetic acid concentration; these values returned to normal shortly after weight recovery. The CSF level of norepinephrine (NE) in underweight anorectics and in these patients a few weeks after weight restoration was similar to that in normal subjects. Long-term weight-recovered (20 +/- 7 months) anorectics, however, had a 50% decrease in CSF NE level compared with that of controls. Underweight anorectics have state-associated disturbances in dopamine and serotonin metabolism. Changes in NE metabolism are more complex and state independent. These abnormalities in neurotransmitter metabolism are part of the neurobiological syndrome of anorexia nervosa and may contribute to the characteristic changes in mood, behavior, and neuroendocrine function.