A study was undertaken of fasting and post-prandial blood levels of glucose and a number of gastrointestinal hormones in patients with anorexia nervosa. After an overnight fast their blood levels of glucose, insulin and pancreatic glucagon were significantly lower than those of age-sex matched healthy volunteers. There were no significant differences in the levels of gastrin, total glucagon-like immunoreactivity, vasoactive intestinal polypeptide, pancreatic polypeptide, secretin and gastric inhibitory polypeptide. Serial blood samples were taken for up to two hours after the ingestion of a standard mixed meal (450 kcal) and these showed a significant glucose intolerance, a reduced and delayed insulin response, and a reduced release of gastric inhibitory polypeptide, as compared with the controls. There was an increased release of pancreatic polypeptide but the difference in the post-prandial hormone profile between patients and controls for gastrin did not reach statistical significance.