The origin of spermine, which tends to increase in sera of cancer patients, was studied in relation to the internal pancreatic secretion and alkalinephosphatase and obtained following results. 1) Action of extrinsic insulin: Elevation of serum spermine level was observed at prespastic stage in rabbits injected Insulin 2 units per kilo-gram. 2) Action of intrinsic insulin: On applying the experiment of B-cell destruction of Langerhans' islets followed by excessive production of insulin at early stage, serum spermine increased remarkably with compared to the experiment 1). Serumspermine level was also higher for consideable time in sugar-loading test resulting increase of insulin demand. 3) Serum spermine was not specifically related to the blood sugar and alkalinephosphatase of cancer patients.