Using the new enzymatic assay for isolation and determination of polyamine in blood presented in Report 4, the polyamines in the blood were isolated and determined in 84 patients with genitourinary cancer. In the early diagnosis, the positive rates of each fraction were not so high, but, relatively high positive rates were demonstrated, when any one of the polyamines were found positive: namely, 85.7% in renal cell cancer, 66.7% in renal pelvic and ureteral cancer, 44.0% in bladder cancers. These results seem to support the usefulness of the new method, and encourage further investigation of polyamines in the blood as tumor markers.