The polyamines, putrescine, spermidine, and spermine have been established as biochemical markers of normal and pathological growth. In malignancy, the urinary concentrations of spermidine reflect the tumor cell loss and the urinary level of putrescine is related both to the number of tumor cells in cell cycle and to the tumor cell loss factor. A greater than twofold increase in urinary spermidine within 72 hr of chemotherapy predicts a complete or a partial response with a high degree of accuracy. Urinary putrescine may be valuable, not only in assessing the early response to therapy but also in determining whether the chemotherapy promotes a later burst of cell proliferation. Erythrocyte spermidine concentrations also appear to track alterations in tumor kinetics. Alterations in intracellular and extracellular polyamines in other pathologies such as psoriasis, muscular dystrophy, and cystic fibrosis also accurately reflect the disease activity and, in those cases studied, response to therapy. Therefore, the determination of polyamine concentrations in extracellular fluids and in erythrocytes allows for (1) the early assessment of response to multimodality therapy, (2) disease or tumor staging, and (3) assessment of disease activity including long-term monitoring of polyamine concentrations to pinpoint remission and relapse in adjuvant patients. Information obtained by the monitoring of polyamines could result in prolongation of survival time of patients as well as assist in the design of the most effective therapy regimen for the pathology. Since other such specific kinetic markers are not available, polyamines should be clinically utilized to track tumor evolution and tumor response to therapy in those patients at high risk, in which such measurements could be translated into therapeutic efficacy.