Nuclear Magnetic Resonance Spectroscopy provides a non-invasive method for monitoring tumor bioenergetics and response to therapy. The 31 P spectrum appears to be an indicator of tumor bioenergetics, reflecting its extent of perfusion and degree of oxygenation. During growth, the level of high energy phosphates generally decreased while the level of low energy phosphates generally increased. This has been attributed to the development of vascular insufficiency. Tumor responses to chemotherapy, radiation therapy and hyperthermia appear to be accompanied by significant 31 P spectral changes. Specific metabolic pathways have been examined by 13 C NMR studies employing isotropically labeled metabolites. Detection of 1H compounds holds considerable promise for application to experimental, clinical oncology.