We recruited 10 patients with anorexia nervosa and 6 age- and height-matched control subjects. Basal and postprandial concentrations of glucose, insulin, cholesterol, amino acids, gastrin, and pancreatic polypeptide (PP) were measured in response to a standard mixed meal. The only satiety signal that was significantly different between the anorectic group and the control group was PP (P less than 0.001). Tryptophan-LNAA and tyrosine-LNAA ratios were not significantly different in the two groups; however, there was a trend toward a lower tryptophan-LNAA ratio in the anorectic group. Gastrin concentrations were significantly decreased in the anorectic group (P less than 0.001) as were basal insulin concentrations (P less than 0.05). Decreased gastrin concentrations may play a role in the gastric symptoms associated with anorexia nervosa. Previous findings that PP release is diminished in obesity, together with the present findings of PP increase in anorexia nervosa, suggest that this peptide may play a role in appetite control mechanisms.