CSF concentrations of serotonin and dopamine metabolites in 16 patients with anorexia nervosa were measured before and after probenecid administration, and the patients were studied before and at intervals after weight recovery. After probenecid administration, the weight-recovered nonbulimic anorexic patients had a higher concentration of the serotonin metabolite, 5-hydroxyindoleacetic acid, than the weight-recovered bulimic patients but no significant differences in CSF homovanillic acid. This finding is consistent with evidence that suggests a role for brain serotonin metabolism in carbohydrate and mood regulation.