In the serum and saliva of 45 patients with eating disorders and in 30 normal controls, alpha-amylase activity and isoamylase levels were measured. Of the 45 patients evaluated, 12 had restrictive anorexia nervosa, 13 were bulimic anorectics and 20 had bulimia nervosa. In all these groups, the mean alpha-amylase values in serum and saliva were higher than that of the control group. The proportion of pancreatic (P)- and salivary (S)-alpha-amylase isoenzymes in serum were within the normal range for the patient group with restrictive anorexia nervosa, whereas the bulimic anorexia nervosa and bulimia nervosa patients showed significantly greater increases in S- than P-isoamylase activity. The correlation of the salivary alpha-Amylase isoenzym pattern in serum and saliva pointed to the salivary glands as origin of the elevated salivary isoamylase levels in serum. Hyperamylasemia was found in 10 (25%) of the 45 patients with eating disorders. Three of these patients showed besides an increased S-alpha-amylase activity also pathologically elevated P-alpha-amylase and lipase activity in serum; however there were no abdominal symptoms, laboratory data or ultrasonic signs of pancreatitis. In all patients with eating disorders, the mean concentration and secretion of alpha-amylase in saliva were increased. Swelling of the salivary glands was present in 14 patients. In these cases the percentage of salivary-isoamylase activity in total serum alpha-amylase activity was increased significantly, whereas the alpha-amylase secretion in the resting saliva was decreased.