For the purpose of studying a mechanism of quantitative increase of serum spermine, the author has examined the spermine reaction of patients bearing tumor and studied, in animal experiments, the relation between cancer toxin and serum spermine, in cases of viscera damaged. Results obtained are as follows. 1) Serum spermine reaction was positive in 86 per cent (including false positive) of 69 cases of cancer patients, and in 35 per cent of cases bearing non-cancerous tumor. 2) Serum spermine had no relation to serum protein in cancer patients, and showed no differences in cancers different histologically. 3) A factor increasing serum spermine was present in cancer extract, urine of cancer patients, and toxohormone which containes so-called cancer toxin. 4) The pancreas, liver, adrenal gland and reticuloendothelial system were thought to be related to the metabolism of serum spermine. From the facts described above, it is presumed that the serum spermine would be increased following disorders of the pancreas, liver, adrenal gland and reticuloendothelial system caused by cancer toxin.