The concentration and its dynamics of the amin acid in serum and pancreatic juice were observed comparatively among the diabetics the chronic pancreatitis and the pancreas cancer, together with the endocrine and exocrine function of pancreas. Patients with the chronic pancreatitis and/or the pancreas cancer were pointed out their abnormal exocrine function of the pancreas. On the contrary, the diabetics was proved to have an abnormal endocrine function and a disorder of the free amino acid metabolism in serum and pancreas juice, as followed. 1. Glutamic acid, valine and lysine were highly increased in the fasting serum amino acid of the diabetics. The dynamic change of amino acid concentration fluctuated more strongly in the course after P-S stimulation of the diabetics than of the normal control. 2. The time at which the concentration of amino acid would reach the maximal level, delayed significantly in the pancreas cancer as well as in the diabetics. Alternatively, in the chronic pancreatitis all the amino acids diminished their concentraion in pancreas juice. 3. In regard with the concentration of the free amino acid recovered from pancreas juice after P-S stimulation, the diabetics reduced all of them other than alanine, glutamic acid and lysine which were inversely increased.