To avoid the confounding influences of malnutrition or weight loss, we studied patients with anorexia nervosa at normal weight and stable dietary intake. Compared with 15 controls, 17 long-term weight-restored anorectic subjects had elevated concentrations of cerebrospinal fluid 5-hydroxyindoleacetic acid, the major serotonin metabolite, whereas levels of cerebrospinal fluid homovanillic acid, the major dopamine metabolite, were normal. Elevated levels of cerebrospinal fluid 5-hydroxyindoleacetic acid may indicate increased serotonin activity. Such activity could contribute to pathological feeding behavior. Most importantly, this study raises the question as to whether increased cerebrospinal fluid 5-hydroxyindoleacetic acid levels are associated with overly inhibited, anxious, or obsessive traits.